Question

The divisibility rule of 7 states that if a number is divisible by 7 then the last digit doubled and subtracted from the remaining number should be 0 or divisible by ___.

Answer 1

The divisibility rule of 7 states that if a number is divisible by 7 then the last digit doubled and subtracted from the remaining number should be 0 or divisible by 7.
For example, 21: (1 $\times$ 2) = 2 and 2 - 2 = 0; Hence 21 is divisible by 7
Also, 98 : (8 $\times$ 2) = 16 and 16 - 9 = 7. 7 is divisible by 7. Hence 98 is divisible by 7