Provide a fast way to multiply a number by 31

Left shift the number by 5 bits and subtract the number once. For e.g., If the number is 10 left shift by 5 bits gives.

Left Shift by 1 bit is multiplication by 2
Left Shift by 5 bits is multiplication by 32

Since we need to multiply by 31 what we do is multiply the number by 32 and subtract the number once.