Question

What is 81-16 using mental math

Answer 1

I know in my head that 16=20-4
so -16=-20+4


so 81-16 really means 81-20+4
I can first subtract 20 from 81 to get 61
then add 4 to get 65
that's my mental process to get 81-16 without writing anything down

Answer 2

81 - 16 = 65 because

80 - 15 = 65

(you just subtract 1 from both 81 and 16 to get easier numbers to minus)

hope this helps