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In this Class 10 Mathematics topic from the chapter Real Numbers, students learn that every integer greater than 1 can be expressed as a product of prime numbers, and that this prime factorisation is unique apart from the order of the factors. They practise finding prime factors and use the theorem to understand and determine the HCF and LCM of numbers. The topic builds clear reasoning about the structure of whole numbers and supports later work with divisibility and number relationships.
TOPIC PRACTICE
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Hard · Level 4 · hcf,powers,hardView options
0
1
2
3
Hard · Level 4 · prime-factorisation,perfect-square,hardView options
(3^4\times7^2)
(3^2\times7^4)
(3^3\times7^3)
(63\times63)
Hard · Level 4 · perfect-cube,prime-exponents,hardView options
(2\times3\times5^2)
(2^2\times3\times5)
(2\times3^2\times5)
(2^2\times3^2\times5^2)
Hard · Level 4 · perfect-square,division,hardView options
2
3
6
7
Hard · Level 4 · product-factorisation,powers,hardView options
3
4
5
6
Hard · Level 4 · product-factorisation,powers,hardView options
5
6
8
10
Hard · Level 4 · distinct-prime-factors,prime-factorisation,hardView options
2, 3, 5, 7 and 11
2, 3, 5 and 7
3, 5, 7 and 11
2, 5, 7 and 13
Hard · Level 4 · hcf,prime-factorisation,hardView options
132
264
396
660
Hard · Level 4 · lcm,prime-factorisation,hardView options
43560
21780
87120
14520
Hard · Level 4 · hcf-lcm-relation,powers,hardView options
2
3
4
5
Hard · Level 4 · hcf-lcm-relation,powers,hardView options
0
1
2
3
Hard · Level 4 · prime-factorisation,powers,hardView options
(7^4)
(7^3)
(49^2)
(7\times343^2)
Hard · Level 4 · perfect-cube,division,prime-exponentsView options
(2^2\times3^2)
(2\times3^2)
(2^2\times3)
(3^2\times5)
Hard · Level 4 · evaluate-factorisation,prime-factors,hardView options
2520
1260
5040
840
Hard · Level 4 · hcf-lcm-relation,conceptual,hardView options
(ab)
(a+b)
(a-b)
1
Hard · Level 4 · hcf,lcm,ratio,hardView options
12
24
36
48
Hard · Level 4 · product-factorisation,counting-powers,hardView options
10
11
12
13
Hard · Level 4 · lcm,powers,hardView options
1
2
3
4
Hard · Level 4 · hcf,powers,hardView options
1
2
3
4
Hard · Level 5 · fundamental-theorem-arithmetic,unique-factorisation,hardView options
The order may change but the prime factors do not change
Every number has only one factor
Every number has only two prime factors
Every number is itself prime
Question 1HardLevel 4
If (a=2^2\times3^3\times5) and (b=2^4\times3\times5^2), what is the power of 5 in the HCF of (a) and (b)?
Correct answer: B
Step 1: In HCF, take the smaller power of the common prime. Step 2: The powers of 5 are 1 and 2. Step 3: The smaller power is 1, so the answer is 1.
If a number has prime factorisation (2^5\times3^2\times5^4), what is the smallest number by which it must be multiplied to make a perfect cube?
Correct answer: B
Step 1: For a perfect cube, exponents must be multiples of 3. Step 2: We need (2), (3), and (5^2) to make the powers (6,3,6). Step 3: The smallest multiplier is (2\times3\times5^2).
By which smallest number should 3528 be divided to get a perfect square?
Correct answer: C
Step 1: (3528=72\times49=2^3\times3^2\times7^2). Step 2: For a perfect square, all exponents must be even, but the exponent of 2 is 3. Step 3: Dividing by 2 gives (2^2\times3^2\times7^2), so the smallest number is 2.
If (x=2^4\times3^2\times7) and (y=2^2\times3^3\times5), what will be the power of 3 in (xy)?
Correct answer: C
Step 1: In multiplication, add the exponents of the same prime base. Step 2: The power of 3 in (x) is 2 and in (y) is 3. Step 3: In (xy), the power of 3 is (2+3=5).
If (a=2^3\times3^2\times11) and (b=2^2\times3\times5\times11^2), what is the HCF of (a) and (b)?
Correct answer: A
Step 1: The common prime factors are 2, 3, and 11. Step 2: The smaller powers are (2^2), (3^1), and (11^1). Step 3: (4\times3\times11=132), so the HCF is 132.
If (a=2^3\times3^2\times11) and (b=2^2\times3\times5\times11^2), what is the LCM of (a) and (b)?
Correct answer: A
Step 1: For LCM, take the highest powers of all prime factors. Step 2: The highest powers are (2^3), (3^2), (5), and (11^2). Step 3: (8\times9\times5\times121=43560), so the answer is 43560.
If the HCF of two numbers is 30 and their LCM is 2310, what is the power of 11 in their product?
Correct answer: B
Step 1: The product is (30\times2310). Step 2: 30 has no factor 11 and (2310=2\times3\times5\times7\times11). Step 3: Therefore, the power of 11 in the product is (0+1=1).
If (n=2^2\times3^5\times5^3), by which smallest number should (n) be divided to make it a perfect cube?
Correct answer: A
Step 1: In a perfect cube, each exponent must be a multiple of 3. Step 2: (2^2) and (3^5) cause the issue; reduce them to 0 and 3. Step 3: Dividing by (2^2\times3^2) gives exponents (0,3,3).
Which option gives the number formed by (2^3\times3^2\times5\times7)?
Correct answer: A
Step 1: First calculate (2^3=8) and (3^2=9). Step 2: (8\times9\times5\times7=2520). Step 3: To get the number from prime factorisation, multiply all factors.
If (a=2^4\times3^2\times5) and (b=2^3\times3\times5^2), the product of their HCF and LCM will be equal to what?
Correct answer: A
Step 1: For two numbers, HCF (\times) LCM equals the product of the two numbers. Step 2: This also follows from prime powers because the smaller and higher exponents together give the total exponent. Step 3: Therefore, the answer is (ab).
If (x=2^2\times3^3\times5) and (y=2^4\times3\times5^2), how many prime factors will (xy) have if repetition is counted?
Correct answer: D
Step 1: In (xy), exponents of the same bases are added. Step 2: Powers become (2^{6}), (3^{4}), and (5^{3}). Step 3: Counting with repetition gives (6+4+3=13).
In the Fundamental Theorem of Arithmetic, prime factorisation of a number is called unique. What does this correctly mean?
Correct answer: A
Step 1: Uniqueness means the set of prime factors remains fixed. Step 2: Changing the order does not change the product, so (2\times3\times5) and (5\times3\times2) are the same prime factorisation. Step 3: In exams, do not treat order change as a different answer.
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