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In this Class 9 Mathematics topic from Number Systems, students explore the square root spiral, a geometric construction that represents √2, √3, √4 and successive square-root lengths. They learn how right triangles and the Pythagorean theorem generate each new radius, connect these constructions with irrational numbers, and locate their values on the number line. The topic strengthens understanding of square roots, geometric representation, measurement, and the relationship between numerical patterns and visual reasoning.
TOPIC PRACTICE
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Easy · Level 6View options
√5
√6
√7
√12
Easy · Level 6View options
\(\sqrt{5}\)
\(\frac{3}{2}\)
\(\frac{7}{3}\)
\(\pi\)
Easy · Level 6View options
One unit
Two units
Half of the preceding hypotenuse
Equal to the preceding hypotenuse
Easy · Level 6View options
√13
√14
√15
√16
Easy · Level 6View options
प्रत्येक नए समकोण त्रिभुज में एक भुजा 1 इकाई और दूसरी लंब भुजा पिछले त्रिभुज का कर्ण होती है।
सर्पिल के सभी त्रिभुज समबाहु होते हैं।
सर्पिल में बनने वाले सभी कर्णों की लंबाई समान होती है।
प्रत्येक नए त्रिभुज की दोनों लम्ब भुजाएँ बराबर होती हैं।
Easy · Level 6View options
Hypotenuse of (\sqrt{2})
Hypotenuse of (\sqrt{3})
(3) unit line
(1) unit perpendicular
Easy · Level 6View options
A perpendicular segment of length 1 is drawn at an endpoint of the previous hypotenuse.
A segment of length 1 is drawn parallel to the previous hypotenuse.
Both legs of every new triangle are kept 1 unit long.
The hypotenuse of every new triangle is kept 1 unit long.
Easy · Level 6View options
To construct a right angle
To measure the length of the hypotenuse
To remove the square root symbol
To find the decimal expansion
Easy · Level 6View options
पिछले त्रिभुज के कर्ण के अंतिम बिंदु पर, उसके लंबवत
पिछले त्रिभुज के कर्ण के समानांतर
पहले बने 1 इकाई के रेखाखंड के विस्तार में
पिछले त्रिभुज के आधार के मध्यबिंदु से
Easy · Level 6View options
(\sqrt{78})
(\sqrt{79})
(\sqrt{80})
(\sqrt{81})
Easy · Level 6View options
\(\sqrt{11}\)
\(\sqrt{20}\)
\(11\)
\(\sqrt{9}\)
Easy · Level 6View options
Draw a (1) unit perpendicular at the end of (\sqrt{2})
Erase the segment
Make the denominator zero
Convert the triangle into a square
Easy · Level 6View options
Perpendicular to the previous hypotenuse
Parallel to the previous hypotenuse
Along the angle bisector of the previous hypotenuse
Along the extension of the previous hypotenuse
Easy · Level 6View options
इकाई लंबाई के दो परस्पर लम्बवत भुजाओं वाले समकोण त्रिभुज के कर्ण के रूप में
भुजा 2 इकाई वाले वर्ग के विकर्ण के रूप में
2 इकाई लंबाई वाले रेखाखंड के रूप में
इकाई त्रिज्या वाले वृत्त की परिधि के रूप में
Easy · Level 6View options
पिछली कर्ण के समानांतर एक इकाई लंबाई की भुजा बनाकर
पिछली कर्ण पर लंबवत एक इकाई लंबाई की भुजा बनाकर
पिछली कर्ण को दो बराबर भागों में बाँटकर
पिछली कर्ण के बराबर लंबाई की दूसरी भुजा बनाकर
Easy · Level 6View options
\(\sqrt{9}\)
\(\sqrt{16}\)
\(\sqrt{25}\)
\(\sqrt{7}\)
Easy · Level 6View options
So that, by Pythagoras’ theorem, the next hypotenuse becomes the square root of the next natural number.
So that each new triangle becomes an equilateral triangle.
So that all hypotenuses remain 1 unit long.
So that all angles in the spiral are acute.
Easy · Level 6View options
\(\sqrt{2}\) units
\(2\) units
\(1\) unit
\(\sqrt{3}\) units
Easy · Level 6View options
The new perpendicular side must be 1 unit; with the previous hypotenuse \(\sqrt{16}\), it forms \(\sqrt{17}\)
The new perpendicular side must be \(\sqrt{17}\) units
\(\sqrt{17}\) cannot be represented on a square root spiral
The new perpendicular side must be 16 units
Easy · Level 6View options
(\sqrt{55})
(\sqrt{56})
(\sqrt{57})
(\sqrt{58})
Easy · Level 6View options
(\sqrt{42})
(\sqrt{43})
(\sqrt{44})
(\sqrt{86})
Easy · Level 6View options
Ruler
Clock
Calculator
Balance
Easy · Level 6View options
Set square — to construct a 90° angle
Calculator — to draw an arc
Balance — to transfer the hypotenuse
Clock — to measure 1 unit
Easy · Level 6View options
√1 → √2 → √3 → √4
√1 → √3 → √4
√2 → √4 → √3
√4 → √3 → √2
Easy · Level 6View options
√64, 8
√62, no whole number
√64, 7
√126, no whole number
Question 1EasyLevel 6
If a new hypotenuse is made from √6 in a square root spiral, which hypotenuse is obtained?
Correct answer: C
A square root spiral uses a right triangle at every stage, adding a new perpendicular side of length 1 unit to the existing hypotenuse. If the existing hypotenuse is √6 and the new hypotenuse is h, the Pythagorean theorem gives h²=(√6)²+1²=6+1=7. Since h is a positive length, h=√7. Therefore option C is correct. √5 is the preceding member of the sequence, while √6 is the old hypotenuse already present, not the newly obtained one. √12 is incorrect because the added side contributes 1², not another 6 or a multiplication by 2. The construction therefore increases the squared hypotenuse from 6 to 7 and moves from √6 to √7.
In a square root spiral made by constructing successive right triangles with unit-length sides, which of the following lengths can be represented by a line segment?
Correct answer: A
Each new right triangle in a square root spiral adds a unit side. If the previous hypotenuse is \(\sqrt{4}\), Pythagoras gives the next hypotenuse as \(\sqrt{4+1}=\sqrt{5}\). \(\pi\) is not obtained in this sequence. Exam tip: remember the hypotenuse pattern \(\sqrt{2},\sqrt{3},\sqrt{4}\dots\).
In constructing a square root spiral, one side of each new right triangle is the previous hypotenuse. What length is taken for the other perpendicular side?
Correct answer: A
In a square root spiral, a perpendicular side of length 1 unit is added to the previous hypotenuse. Thus, the new hypotenuses represent \(\sqrt{2}, \sqrt{3}, \sqrt{4}\), and so on. Exam tip: the added side is always 1 unit.
Just before constructing √15 in a square root spiral, which hypotenuse will be present?
Correct answer: B
The square root spiral is generated step by step by adding a perpendicular segment of length 1 unit to the current hypotenuse. If the current hypotenuse is √14, then the next hypotenuse h satisfies h²=(√14)²+1²=14+1=15, so h=√15. Therefore the hypotenuse present immediately before constructing √15 is √14, making option B correct. √13 is one stage earlier in the sequence. √15 is the target that is about to be constructed, not the value already present. √16 is the following stage after √15. The essential relationship is that the squared value increases by exactly one at each construction step, so the predecessor of 15 must be 14.
Which statement correctly describes the construction of a square root spiral?
Correct answer: A
In a square root spiral, each new right triangle uses the previous hypotenuse and a new perpendicular side of length 1. Hence the hypotenuses increase, not remain equal. Exam tip: remember \(h_{\text{new}}^2=h_{\text{old}}^2+1\).
For what can a set square be used in a square root spiral?
Correct answer: A
While constructing a square root spiral, each new triangle is formed by drawing a right angle on the previous hypotenuse. A set square helps construct this right angle accurately, so option A is correct. The length of a hypotenuse is generally measured with a ruler; the main use of a set square is constructing angles. Exam tip: at each step of a square root spiral, draw a new unit-length side perpendicular to the previous hypotenuse.
In a square root spiral, where is the new line segment of length 1 drawn to form the next triangle?
Correct answer: A
At each step, a unit segment is drawn perpendicular to the previous hypotenuse at its endpoint. If the previous hypotenuse is \(\sqrt{n}\), Pythagoras gives the next one as \(\sqrt{n+1}\). In exams, check the right-angle mark.
To construct (\sqrt{80}) in a square root spiral, which previous hypotenuse will be used?
Correct answer: B
The direct answer is B, (\sqrt{79}). In each step of the square root spiral, a 1-unit segment is drawn perpendicular to the previous hypotenuse. If that previous hypotenuse is (\sqrt{n}), then the new hypotenuse is (\sqrt{n+1}) because (\sqrt{n})^2+1^2=n+1. For the target (\sqrt{80}), solve (n+1=80); hence (n=79) and the previous hypotenuse is (\sqrt{79}). Option A, (\sqrt{78}), would give (\sqrt{79}) next, so it is one step short. Option B is correct because adding the unit perpendicular gives exactly (\sqrt{80}). Option C, (\sqrt{80}), is the required new hypotenuse, not the previous one. Option D, (\sqrt{81}), would produce (\sqrt{82}), one step beyond the target. The safe exam method is to subtract 1 from the number inside the target square root: (80-1=79).
While constructing a square root spiral, each new right triangle is drawn on the hypotenuse of the previous triangle. If at one stage the hypotenuse is \(\sqrt{10}\) and the new perpendicular side is 1 unit, what will be the hypotenuse of the new triangle?
Correct answer: A
By Pythagoras’ theorem, new hypotenuse² = \((\sqrt{10})^2+1^2=10+1=11\). Hence the new hypotenuse is \(\sqrt{11}\). \(\sqrt{20}\) results from squaring the previous hypotenuse incorrectly. Exam tip: square the radical first.
After constructing (\sqrt{2}) in a square root spiral, what construction is done next?
Correct answer: A
The direct answer is A: draw a 1-unit perpendicular at the end of (\sqrt{2}). The construction works by making a right triangle at every stage. Start with a unit-based triangle to obtain hypotenuse (\sqrt{2}). Next, keep (\sqrt{2}) as one side and draw a perpendicular side of 1 unit. Pythagoras gives the new hypotenuse (\sqrt{(\sqrt{2})^2+1^2}=\sqrt{3}). Option A is correct because this is exactly the next construction needed. Option B, erasing the segment, destroys the construction and cannot create the next square root. Option C, making a denominator zero, is unrelated to a geometric spiral and division by zero is not permitted. Option D, converting the triangle into a square, is not the method; the next value is created by a new right triangle, not by making a square. The word “perpendicular” means meeting at a right angle of 90 degrees. Memory cue: at every new endpoint, add one unit at a right angle; the hypotenuse then moves from (\sqrt{n}) to (\sqrt{n+1}).
While constructing a square root spiral, a student draws the new side in the same direction from the endpoint of the previous hypotenuse. How should the new unit-length side be drawn to keep the spiral correct?
Correct answer: A
Each added triangle must be right-angled. Drawing a unit side perpendicular to the previous hypotenuse gives the next hypotenuse using Pythagoras’ theorem. A parallel side does not form a right angle. Exam tip: mark the new unit side perpendicular first.
How is \(\sqrt{2}\) represented in a square root spiral?
Correct answer: A
The first right triangle in a square root spiral has perpendicular sides of 1 unit and 1 unit. By Pythagoras, hypotenuse² = 1² + 1² = 2, so the hypotenuse is \(\sqrt{2}\). A square of side 2 has diagonal \(2\sqrt{2}\), not \(\sqrt{2}\). Exam tip: identify the triangle’s legs first.
While constructing a square root spiral, how is each new right-angled triangle formed using the hypotenuse of the previous triangle?
Correct answer: B
In each new triangle, the previous hypotenuse is one leg and a unit segment is drawn perpendicular to it. By Pythagoras, the square of the new hypotenuse increases by 1. Exam tip: each added segment is perpendicular to the previous hypotenuse.
In a square root spiral, which of the following lengths represents an irrational number?
Correct answer: D
Since 7 is not a perfect square, \(\sqrt{7}\) is irrational and is shown as a distinct length on the spiral. In contrast, \(\sqrt{9}=3\), \(\sqrt{16}=4\), and \(\sqrt{25}=5\) are rational. Exam tip: square roots of perfect squares are integers.
Why is one side of each new right triangle kept 1 unit long while constructing a square root spiral?
Correct answer: A
The first hypotenuse is \(\sqrt{2}\). Adding a new 1-unit side gives hypotenuse squared as \(2+1=3\), so the next hypotenuse is \(\sqrt{3}\). Exam tip: each added triangle is right-angled.
While constructing a square root spiral, a student takes a right triangle with one side of length 1 unit and the other perpendicular side also 1 unit. What is the length of its hypotenuse?
Correct answer: A
By Pythagoras’ theorem, hypotenuse² = 1² + 1² = 2, so the hypotenuse is \(\sqrt{2}\) units. Option 2 is only the sum of the sides, not the hypotenuse. Exam tip: add squares, then take the square root.
A student says that to represent \(\sqrt{17}\) on a square root spiral, a perpendicular side of length 4 units should be drawn because \(17-1=16\). Why is this statement incorrect?
Correct answer: A
In a square root spiral, each new right triangle uses the previous hypotenuse and a new side of 1 unit. Since \(\sqrt{16}^2+1^2=16+1=17\), the new hypotenuse is \(\sqrt{17}\). A side of 4 gives \(16+16=32\), not 17. Exam tip: check the sum of squares using Pythagoras' theorem.
In a square root spiral, which hypotenuse will be formed after (\sqrt{43})?
Correct answer: C
The square-root spiral advances by one under the radical at every stage. The construction uses the current hypotenuse and a new perpendicular segment of length 1. If the current hypotenuse is sqrt{n}, then the next hypotenuse has square length n+1, so its length is sqrt{n+1}. This is a direct application of the Pythagorean theorem.
Here the current value is sqrt{43}. Adding the square of the new unit side gives (sqrt{43})^2+1^2=43+1=44. Taking the positive square root, as lengths are positive, gives sqrt{44}. Therefore option C is correct. sqrt{42} is the preceding stage, while sqrt{43} is the existing hypotenuse, not the new one. There is no doubling in this process.
Which tool and its use are correctly matched for constructing a square-root spiral?
Correct answer: A
A square-root spiral is constructed through successive right triangles. A set square is a suitable geometrical instrument for drawing or checking a 90° angle, which is essential before applying the Pythagorean theorem. Thus option A correctly matches the tool with its use. A calculator performs numerical operations but cannot physically draw an arc. A balance measures mass, not a line segment or hypotenuse, so option C is inappropriate. A clock measures time and has no role in measuring a 1-unit length; a ruler or compass would be relevant for that purpose. The correct match is therefore the set square and right-angle construction.
What is the correct order of hypotenuses for reaching √4 in a square-root spiral?
Correct answer: A
Answer: option A, √1 → √2 → √3 → √4. The spiral begins with a unit length, represented as √1. Add a perpendicular unit segment: the new hypotenuse has square 1 + 1 = 2, so it is √2. Repeat the same construction: (√2)² + 1² = 2 + 1 = 3, giving √3. One more step gives (√3)² + 1² = 3 + 1 = 4, giving √4. Therefore the complete order is √1, √2, √3, √4. Option B skips the necessary √2 stage. Option C places the stages in an incorrect order, and option D reverses the construction. Each new hypotenuse depends on the immediately previous one, so no stage may be skipped. Memory cue: write the radicands in consecutive order: 1, 2, 3, 4.
After constructing √63 in a square-root spiral, what is the next hypotenuse and what whole number does it equal?
Correct answer: A
The governing rule is the one-unit progression of the standard square-root spiral. If the present hypotenuse is √n, adding a perpendicular of length 1 gives a new hypotenuse h with h²=n+1. Therefore, after √63, the next hypotenuse is √64. Because 64=8², its principal square root is exactly 8, a whole number. Hence option A correctly states both the radical and its value. Option B goes backward to √62 rather than forward. Option C identifies √64 but evaluates it incorrectly as 7; 7²=49, whereas 8²=64. Option D doubles the radicand without justification and does not follow the spiral rule. The fact that 64 is a perfect square explains why this next length is an integer.
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