If the 11-digit number 89x6402087y is divisible by 72, then what is the value of (2x - y)?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 14.
72 = 8 × 9
Divisibility rule of 8: if its last three digits are divisible by 8.
⇒ 87y ÷ 8
⇒ y = 2
Divisibility rule of 9: the sum of its digits is divisible by 9
⇒ 8 + 9 + x + 6 + 4 + 0 + 2 + 0 + 8 + 7 + 2 = 46 + x
⇒ x = 8
So, (2x - y) = 2 × 8 - 2 = 16 - 2 = 14