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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
Quiz this set
Up to 20 questions from this page. Select your focus, then start.
If a number has prime factorisation (2^{10}\times3^7\times5^2\times11^3\times13), how many distinct prime factors does it have?
Correct answer: A
Step 1: When counting distinct prime factors, do not add exponents. Step 2: The prime bases are 2, 3, 5, 11, and 13. Step 3: Therefore, the number of distinct prime factors is 5.
If the two numbers are (2^7\times3^3\times11) and (5^4\times7^2\times13), which statement about them is correct?
Correct answer: A
Step 1: The prime factors of the first number are 2, 3, and 11. Step 2: The prime factors of the second number are 5, 7, and 13. Step 3: There is no common prime factor, so they are co-prime.
Step 1: Recognise (176400=420^2). Step 2: Since (420=2^2\times3\times5\times7), (420^2=2^4\times3^2\times5^2\times7^2). Step 3: In a perfect square, every prime exponent is even.
If (n=2^6\times3^5\times5^2\times17), by which number must (n) be divisible?
Correct answer: A
Step 1: (20655=3^5\times5\times17). Step 2: All these prime factors are present in (n) with sufficient powers. Step 3: Therefore, (n) must be divisible by 20655.
If (n=2^8\times3^4\times5^2), by which of the following will (n) not be divisible?
Correct answer: D
Step 1: In (n), the powers are (2^8), (3^4), and (5^2). Step 2: (3375=3^3\times5^3), which needs power 3 of 5. Step 3: Since (n) has only (5^2), (n) is not divisible by 3375.
Which option gives the correct value of (2^9\times3^4\times5)?
Correct answer: A
Step 1: Calculate (2^9=512) and (3^4=81). Step 2: (512\times81\times5=207360). Step 3: In larger products, simplifying powers first is the right method.
If a number has prime factorisation (2^{10}\times3^5\times5^4), what is the smallest number by which it must be multiplied to make a perfect cube?
Correct answer: A
Step 1: For a perfect cube, exponents must be multiples of 3. Step 2: Make (2^{10}), (3^5), and (5^4) into powers 12, 6, and 6. Step 3: The smallest multiplier is (2^2\times3\times5^2).
By which smallest number should 63504 be divided to get a perfect square?
Correct answer: B
Step 1: (63504=16\times3969=2^4\times3^4\times7^2). Step 2: All exponents are even, so the number is already a perfect square. Step 3: The smallest divisor should be 1, but 1 is not listed; therefore no given option is correct.
If (x=2^6\times3^3\times7^4) and (y=2^4\times5^2\times7^5), what will be the power of 7 in (xy)?
Correct answer: C
Step 1: In multiplication, exponents of the same prime base are added. Step 2: The power of 7 in (x) is 4 and in (y) is 5. Step 3: In (xy), the power of 7 is (4+5=9).
If (x=2^8\times3^4\times5) and (y=2^7\times3^2\times11), what will be the power of 2 in (xy)?
Correct answer: C
Step 1: Powers of the same base 2 are added in multiplication. Step 2: The power of 2 in (x) is 8 and in (y) is 7. Step 3: The total power is (8+7=15).
If (a=2^6\times3^3\times11^2) and (b=2^4\times3^5\times5^2\times11), 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 (2^4), (3^3), and (11^1). Step 3: (16\times27\times11=4752), so the HCF is 4752.
If (a=2^6\times3^3\times11^2) and (b=2^4\times3^5\times5^2\times11), 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 (2^6), (3^5), (5^2), and (11^2). Step 3: (64\times243\times25\times121=47044800), so the correct value is 47044800.
If the HCF of two numbers is 180 and their LCM is 25200, what is the power of 2 in their product?
Correct answer: B
Step 1: The product is (180\times25200). Step 2: (180=2^2\times3^2\times5) and (25200=2^4\times3^2\times5^2\times7). Step 3: The power of 2 in the product is (2+4=6).
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