Find the HCF using prime powers Compute the highest common factor (HCF) of 2^3, 3^2, and 15 by interpreting the compressed notation correctly.
-
A23
-
B32
-
C1
-
D360
-
E3
Answer
Correct Answer: 1
Explanation
Introduction / Context:The raw stem “2 3, 3 2 and 15” is a compressed way to denote powers: 2^3 and 3^2, along with 15. We must carefully recover the intended values to apply HCF rules correctly.
Given Data / Assumptions:
- Numbers: 2^3 = 8, 3^2 = 9, and 15.
- All are positive integers.
Concept / Approach:HCF requires the common prime factors with the smallest exponents across all numbers. If there is no prime common to all, the HCF is 1.
Step-by-Step Solution:Prime factorisations: 8 = 2^3; 9 = 3^2; 15 = 3 * 5.Compare across all three: there is no prime that appears in all numbers (2 is missing from 9 and 15; 5 is missing from 8 and 9; 3 is missing from 8).Hence HCF = 1.
Verification / Alternative check:Compute gcd sequentially: gcd(8, 9) = 1; then gcd(1, 15) = 1.
Why Other Options Are Wrong:23 and 32 misread the notation as concatenation rather than powers; 360 is a product not a common factor; 3 is not a factor of 8.
Common Pitfalls:Misinterpreting the compressed stem; assuming some non-existent shared factor; forgetting HCF must divide every number.
Final Answer:1