A candy store makes a 13–pound mixture of gummy bears, jelly beans, and gobstoppers. The cost of gummy bears is $1.00 per pound,
jelly beans cost $2.00 per pound, and gobstoppers cost $2.00 per pound. The mixture calls for three times as many gummy bears as jelly beans. The total cost of the mixture is $20.00. How much of each ingredient did the store use? 8 lbs gummy bears, 2 lbs jelly beans, 3 lbs gobstoppers
3 lbs gummy bears, 6 lbs jelly beans, 4 lbs gobstoppers
6 lbs gummy bears, 2 lbs jelly beans, 5 lbs gobstoppers
8 lbs gummy bears, 3 lbs jelly beans, 2 lbs gobstoppers
Let the amount of gummy bears used be x, that of jelly beans y and gobstoppers z, then x + y + z = 13 . . . (1) x + 2y + 2z = 20 . . . (2) x = 3y . . . (3)
Putting (3) into (1) and (2) gives 4y + z = 13 . . . (4) 5y + 2z = 20 . . . (5)
(4) * 2 => 8y + 2z = 26 . . . (6)
(6) - (5) => 3y = 6 y = 2
From (3): x = 3(2) = 6 From (4): 4(2) + z = 13 z = 13 - 8 = 5
Therefore, there were <span>6 lbs gummy bears, 2 lbs jelly beans, 5 lbs gobstoppers</span> in the mixture.