Divisibility by 13

If adding four times of last digit to number formed by remaining digits is divisible by 13,

Then number is divisible by 13

Is 169 divisible by 13?

Four times last digit = 4 × 9 = 36

Remaining digit = 16

Addition = 16 + 36 = 52

Since 52 is divisible by 13

∴ 169 is divisible by 13

Is 247 divisible by 13?

Four times last digit = 4 × 7 = 28

Remaining digit = 24

Addition = 24 + 28 = 52

Since 52 is divisible by 13

∴ 247 is divisible by 13

Is 298 divisible by 13?

Four times last digit = 4 × 8 = 32

Remaining digit = 29

Addition = 29 + 32 = 61

Since 61 is not divisible by 13

∴ 298 is not divisible by 13