MemoryMentor’s Blog

Multiplying two 2 digit numbers where the first digit is the same and the sum of second digits is 10

1. Take two 2 digit numbers which has the same first digit and sum of second digits is 10
2. Multiply the second digits together
3. Multiply the first digit with its next number ( n* (n+1))

For e.g., 42*48

1. The first digit is the same and sum of the second digit adds to 10(2+8)
2. Multiple second digits 2* 8 = 16
_ _ 16
3. Multiply the first digit with its next number 4*5 = 20
2016