For a positive integer b > 1, if the product of two numbers 6344 and 42b8 is divisible by 12, then find the least value of b.
A5
B7
C3
D4
Answer:
D. 4
Read Explanation:
if 12 is divisible by the product then 3 and 4 also divisible
take 6344 the last two number is 44 it is divisible by 4
take 42b8 last two digits are b8 if it is divisible by 4 the b should be 2,4,6,8
checking the divisibility of 3
6344 = 6+3+4+4=17 it is not divisible by 3
so 42b8 should be divisible by 3
4+2+b+8=14+b
14+b divisible by 3
if b=2
16 it is not divisible by 3
if b=4
18 it is divisible by 3
