If a nine-digit number 789x6378y is divisible by 72, then the value of xy is:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 8.
Co prime factors of 72 = 9 and 8.
Divisibility for 8 = the last three digits of a number is divisible by 8.
78y must be divisible by 8.
The possible value of y is 4.
Divisibility for 9 = The sum of the digits of a number must be divisible by 9.
7 + 8 + 9 + x + 6 + 3 + 7 + 8 + 4= 52 + x.
At x = 2 , (52 + x) will become divisible by 9.
x × y = 4 × 2 = 8.