Question

Carl wants to find the product 30×56
.
Which of the following best explains how he can find the product mentally?



He knows that 30÷5
is 6. He then multiplies 6 by 6 to get 36.




He knows that 30×66
is 30. He then subtracts 1 from 30 to get 29.




He knows that 3×6=18
. He then adds 18 and 5 to get 23.




He knows that 30×16
is 5. He then multiplies 5 by 5 to get 25.

Answer 1

The third explanation is closest. Use 30×56 = (3×56)×10. Compute 3×56 = 3×(50+6) = 150+18 = 168, then multiply by 10 to get 1680.