Question

Which is the highest common factor of 20 and 25?

• A. 50
• B. 20
• C. 15
• D. 5

Answer 1

The correct option is D 5

$20=1\times 20$
$20=2\times 10$
$20=4\times 5$

$\therefore$The factors of 20 are 1, 2, 4, 5, 10 and 20.

$25=1\times 25$
$25=5\times 5$

$\therefore$ The factors of 25 are 1, 5 and 25.

The common factors of 20 and 25 are 1 and 5.

Hence, the highest common factor of 20 and 25 is 5.