Question

Helena uses a mixture of compost and topsoil in her garden. She purchased a total of 10 cubic yards of compost and topsoil for $180. If compost costs $25 per cubic yard and topsoil costs $15 per cubic yard, how many cubic yards of topsoil did she purchase?

A.)3
B.)4.5
C.)5.5
D.)7

Answer 1

to make it short, its D

Explanation:

got it right on Edge

Answer 2

7 cubic yard

Explanation:

Let the compost purchased be x cubic yard

And the topsoil purchased be y cubic yard

Hence

x+y=10 ----(A)

Also

Cost incurred in buying compost at a rate of $25 per cubic yards = 25x

Cost incurred in buying topsoil at a rate of $15 per cubic yards = 15y

Total cost incurred = 25x+15y=180

Diving whole equation by 5 we get

5x+3y=36 ----(B)

Multiply A by 3 and subtract it from B

5x+3y=36

- - -

3x+3y=30

_______

2x=6

x=3

Putting this value in A

x+y=10

3+y=10

y=10-3=7

Hence she purchased 7 cubic yards of topsoil.