pushpitkc wrote:

The highest common factor of x and 15 is 3, the highest common factor of x and 140 is 14. Which of the following may be the highest common factor of x and 660?

A. 22

B. 30

C. 33

D. 44

E. 66

Source:

Experts Global15 = 3 * 5

x has 3 but not 5 as a factor.

140 = 2 * 2 * 5 * 7

x has 2 and 7 as factors but not 5 and not 2*2.

So x has 2, 3 and 7 as factors at least but not 5 and not 2*2.

660 = 2 * 2 * 3 * 5 * 11

So the two numbers certainly have 2 and 3 common so their HCF will be 6 at least.

They will not have 2*2 and 5 common since x does not have these as factors.

They could have 11 common too so their HCF will be 6*11 = 66 at the most.

Answer (E)

_________________

[b]Karishma

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