Question

Clodagh and Eva went school supply shopping together. Clodagh bought 3 packs of pencils and 5 notebooks for a total of $18. Eva bought 4 packs of pencils and 4 notebooks for a total of $16.80. How much does a pack of pencils cost? How much does a notebook cost?

Answer 1

each notebook costs $2.70

each pack of pencils costs $1.50

Explanation:

system of equations:

let p = pack of pencils

let n = notebook

3p + 5n = 18

4p + 4n = 16.8

I used the elimination method by multiplying the first equation by 4 and the second equation by -3

4(3p + 5n = 18) = 12p + 20n = 72

-3(4p + 4n = 16.8) = -12p -12n = -50.4

adding the new equations together you get: 8n = 21.6

n = 21.6/8

n = $2.70

solve for 'p':

3p + 5(2.7) = 18

3p + 13.5 = 18

3p = 4.5

p = $1.50