Question

Thomas calculates 9×7 by thinking avout it as 70-7=63. Explain thomas' strategy.

Answer 1

Thomas uses the distributive property 

9 X 7 = (10 X 7) - (1 X 7) 
          = 70 - 7
          = 63

9 groups of 7 is equal to 10 groups of 7 subtract 1 group of 7.

Answer 2

10 x 7 = 70
1 x 7 = 7
9 x 7 = 70 - 7
9 x 7 = 63