Question

Walt and Amy each have the same number of pennies. Walt made equal stacks of 10 pennies with none left over. Amy made equal stacks of 8 pennies with none left over. What is the least number of pennies that each person could have? Explain how you found your answer.

Answer 1

40 coins

Explanation:

Note that

`10=\underline{2} \cdot 5,\\ \\8=\underline{2} \cdot 2\cdot 2.`

To find the least common multiple you have to multiply all common multiplies and then multiply them by all factors that left. Thus,

`LCM(10,8)=\underline{2} \cdot 5\cdot 2\cdot 2=40.`

This means that if Walt and Amy each have 40 coins, then Walt can make 4 stacks with 10 coins in each and Amy can make 5 stacks with 8 coins in each.