Question

Yumi spent $34.15 buying stamps. The number of 56-cent stamps she bought was 10 less than 4 times the number of 41-cent stamps. How many of each did she buy?

Answer 1

Number of 56 cent stamps is 50 and number of 41 cent stamps is 15

Solution:

Let "a" be the number of 56 cent stamps

Let "b" be the number of 41 cent stamps

The number of 56-cent stamps she bought was 10 less than 4 times the number of 41-cent stamps

number of 56-cent stamps = 4 times the number of 41-cent stamps - 10

a = 4b - 10 -------- eqn 1

Yumi spent $34.15 buying stamps

Therefore,

`56 * a + 41 * b = 3415`

56a + 41b = 3415 ------- eqn 2

Substitute eqn 1 in eqn 2

56(4b - 10) + 41b = 3415

224b - 560 + 41b = 3415

265b = 3975

b = 15

Substitute b = 15 in eqn 1

a = 4(15) - 10

a = 60 - 10

a = 50

Thus number of 56 cent stamps is 50 and number of 41 cent stamps is 15