Question

Describe two different ways that you could find the product 3x990

Answer 1

990 = 1000 - 10

so 3 x 990 = 3 x (1000 - 10) = 3 x 1000 + 3 x (-10) = 3000 - 30 = 2970

and

990 = 900 + 90

so 3 x 990 = 3 x (900 + 90) = 3 x 900 + 3 x 90 = 2700 + 270 = 2970