Question

If three burgers and two fries cost 17.50, and two burgers and three fries cost 15.00, how much does a burger cost?

Answer 1

4.50

Explanation:

If you use x for burgers and y for fries:

1) 3x+2y=17.50

2) 2x+3y=15

You can then do a simultaneous equation by multiplying the first equation by 1.5 to cancel out the y (fries) to get x (burgers) on its own

1) 4.5x+3y=26.25

2) 2x+3y=15

By subtracting the two equations you get 2.5x=11.25

Then divide 11.25 by 2.5, you get x =4.5 so a burger is 4.50

Answer 2

A burger cost 4.50.

Let the cost of a burger be x.

Let the cost of a fries be y.

Since three burgers and two fries cost 17.50, this will be:

3x + 2y = 17.50 ......... i

Since two burgers and three fries cost 15.00, this will be:

2x + 3y = 15.00 .......... ii

Therefore, both equations will be:

3x + 2y = 17.50 ...... i

2x + 3y = 15.00 ....... ii

Multiply equation i by 2

Multiply equation ii by 3

6x + 4y = 35.00 ....... iii

6x + 9y = 45.00 ....... iv

Subtract equation iii from iv

5y = 10.00

y = 10.00/5

y = 2.00

Therefore, the cost of a frie is 2.00

Since the value of a frie has been gotten, it can be put into any of the equation. Using the equation:

3x + 2y = 17.50

3x + 2(2.00) = 17.50

3x + 4.00 = 17.50

3x = 17.50 - 4.00

3x = 13.50

x = 13.50/3

x = 4.50

Therefore, a burger cost 4.50.