Question

Birdseed costs ​$0.57 a pound and sunflower seeds cost ​$0.87 a pound. Angela​ Leinenbachs' pet store wishes to make a 30 pound mixture of birdseed and sunflower seeds that sells for ​$0.81 per pound. How many pounds of each type of seed should she​ use?

Answer 1

Explanation:

x = pounds birdseed

y = pounds sunflower seeds

x + y = 30

0.57x + 0.87y = 30×0.81

with this last trick (to calculate the full cost of the whole 30 pounds based on the targeted individual price per pound) we bring both constraints into the play.

from the first equation we get

x = 30 - y

and we use that in the second equation :

0.57×(30-y) + 0.87y = 30×0.81 = $24.30

17.1 - 0.57y + 0.87y = 24.3

0.3y = 7.2

y = 24

x = 30 - y = 30 - 24 = 6

she uses 6 pounds of birdseed and 24 pounds of sunflower seeds.