Question

Maya buys greeting cards to give to her friends at school. She buys some greeting cards that cost $2.50 each and some greeting cards that cost $4 each. She buys 12 cards in all for a total of $40.50. How many greeting cards that cost $2.50 did Maya buy?

Answer 1

Answer: she bought 5 greeting cards at $2.50 each.

Explanation:

Let x represent the number of greeting cards that she bought at $2.50 each.

Let y represent the number of greeting cards that she bought at $4 each.

She buys some greeting cards that cost $2.50 each and some greeting cards that cost $4 each. She buys 12 cards. This means that

x + y = 12

The total amount that she spent in buying the greeting cards is $40.50. It means that

2.5x + 4y = 40.5- - - - - - - - - - 1

Substituting x = 12 - y into equation 1, it becomes

2.5(12 - y) + 4y = 40.5

30 - 2.5y + 4y = 40.5

- 2.5y + 4y = 40.5 - 30

1.5y = 10.5

y = 10.5/1.5

y = 7

x = 12 - y = 12 - 7

x = 5