We got the addition 27 + 48. The easiest way to do it is to decompose each number. 27 = 20 + 7 48 = 40 + 8 So 27 + 48 = 20 + 7 + 40 + 8 Now you add the numbers that ends with 0 between each others, and the others between each others: 20 + 7 + 40 + 8 = 20 + 40 + 7 + 8 = 60 + 7 + 8 = 60 + 15 =75.
