alleryTo prove a number is divisible by 36, which pair of divisibility tests is enough?
ABy 6 and by 12
BBy 3 and by 12
CBy 2 and by 18
DBy 4 and by 9
Answer & Solution
Correct answer: D. By 4 and by 9
1. Split 36 into 4 x 9, where 4 = 2 squared and 9 = 3 squared hold the full prime powers.
2. A number divisible by both 4 and 9 is divisible by 36.
3. Pairs like 3 and 12 or 2 and 18 share factors and are not sufficient.
_Source: Wikipedia, Divisibility rule, section Composite divisors_
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