Suppose x containers of small popcorn and y containers of large popcorn were sold.
It's given that the total containers sold were 210
which means x+y = 210 .......(1)
Its also given that the total sale cost was $232.50
Which means 0.75xxx + 1.25xxy = 232.50#.....(2)
Now, using equations (1) and (2) find x and y
Use the method of elimination for any one unknown term, either x or y to solve the equations.
However, we can see that neither x or y terms are equal in any of the equations
To make one of the unknown terms equal - say for example, we try to make x terms equal. For that multiply, equation (1) by the coefficient of x which is 0.75 in equation (2)
On, multiplication by 0.75, equation (1) will look like:
0.75xxx+0.75xxy = 0.75xx210
or, 0.75x+0.75y =157.5..............(3)
Now, we can see that the x terms are equal in both equation (2) and equation (3)
Therefore, subtract equation (2) from equation (3)
cancel0.75x+0.75y =157.5
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cancel0.75x + 1.25y = 232.50
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or, cancel-0.5y = cancel-75
or, 0.5y=75
or y = 75/0.5 = 150
Now put the value of y in equation (1) and we can get x.
It would be, x+150 = 210
or x = 210-150 = 60