The number 23a7b is divisible by 45. Find the value of (a + b), if .
select one:
a. 6
b. 4
c. 7
d. 9
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A number is divisible by 45, if it's divisible by 9 and 5!
23a7b = divisible by 5, if b = 0 (or) 5
If b = 0 then 23a7b is divisible when
=>2 + 3 + a + 7 + b
=> 12 + a + 0
=> 12 + a is divisible by 9! It's divisible when a = 6!
If b = 5, then 23a7b is divisible by 9 when =>2 + 3 + a + 7 + b
=>12 + a + 5
=>17 + a is divisible by 9. It's divisible when a = 1
According to options, Answer is A) 6
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