Chapter 4.5, Problem 3P

Suppose that a student has learned the following basic multiplication facts:

 

For each of the multiplication problems (a) through (c), find at least two different ways that some of the preceding fact, together with properties of arithmetic, could be used to mentally calculate the answer to the problem. Explain your answer, drawing arrays to illustrate how the following problems are related to facts in the given lists:

$a.\text{ 6}\times \text{7}$

$b.\text{ 7}\times \text{8}$

$c.\text{ 6}\times \text{8}$