Multiple choice

What is the H.C.F. of 153 and 4913?

  1. 1

  2. 17

  3. 51

  4. 44217

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B Correct answer
Explanation

The prime factorisation of 153 = 3 $\times$ 3 $\times$ 1 ||| |---|---| | 3| 153| | 3| 51| | 17| 17| | | 1|   ||| |---|---| | 17| 4913| | 17| 289| | 17| 17| | | 1|

The prime factorisation of 4913 = 17 $\times$ 17 $\times$ 17 H.C.F (153, 4913) = product of the smallest powers of each common prime factor in the numbers.             = 17

AI explanation

153 factors as 3^2 x 17, and 4913 is exactly 17^3 (17 x 17 x 17). The only prime common to both factorizations is 17, and it appears just once in 153, so the highest common factor is 17.