If the 8-digit number 63k4021p is divisible by 72, then find the value of (5k - 3p).
Show answer & explanation
Correct answer: A
Explanation
The correct answer is Option 1 i.e. 7.
72 = 8 × 9
Divisibility rule of 8: the last three digits must be divisible by 8
⇒ 21p ÷ 8
⇒ p = 6
Divisibility rule of 9: the sum of the digits must be divisible by 9
Sum of digits: 6 + 3 + k + 4 + 0 + 2 + 1 + 6 = 22 + k
⇒ k = 5
Value of (5k - 3p) = (5 × 5 - 3 × 6) = 25 - 18 = 7