Question

When Louisa arranges her pennies into a rectangle with two equal rows, three equal rows, four equal rows, or six equal rows, she has one leftover penny. When she arranges her pennies into a rectangle with five equal rows, she has two leftover pennies. How many pennies could Louisa have? Remember he has between 10 and 40 pennies total.

Answer 1

Answer:

37

Step-by-step explanation:

The answer must be (a multiple of 2, 3, 4 and 6) + 1, and (a multiple of 5) + 1, because 1 or 2 coins were left over when dividing by 2, 3, 4, 6 or 5.

Let's look at the lowest common multiples of 2, 3, 4, 6:

Prime factorisation:

2 = 2

3 = 3

4 = 2 * 2

6 = 2 * 3

therefore, the lowest common multiple is 2 * 2 * 3 = 12

Let's look at the answers that this would give us (ie multiples of 12):

12 + 1 = 13 <-- this would work, but 11 (ie two less than 13) is not a multiple of 5

12 * 2 + 1 = 25 <-- 23 is not a multiple of 5 either

12 * 3 + 1 = 37 <-- 35 (two less than 37) is a multiple of 5 :)

therefore 37 is our answer since it is one more than a multiple of 12 (ie 36) and two more than a multiple of 5 (ie 35)