Question 845847: At McDonald's, four hamburgers and two orders of French fries cost $27.10. Three hamburgers and four orders of fries cost $25.20. If all hamburgers cost the same price and all orders of fries cost the same price, find the price of each.
I'M HELPING MY DAUGHTER WITH HER MATH HOMEWORK, AND DO NOT REMEMBER HOW TO DO THIS! PLEASE HELP! INSTRUCTIONS, EQUATION & STEP - BY - STEP DIRECTIONS ON HOW TO SOLVE THIS PROBLEM WILL BE GREATLY APPRECIATED!
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! At McDonald's, four hamburgers and two orders of French fries cost $27.10.
Three hamburgers and four orders of fries cost $25.20.
If all hamburgers cost the same price and all orders of fries cost the same price, find the price of each.
:
let h = price of the hamburger
let f = price of the fries
:
Write two equations, one for each order
4h + 2f = 27.10
3h + 4f = 25.20
:
We will use elimination here; multiply the 1st equation by 2, subtract the 2nd equation
8h + 4f = 54.20
3h + 4f = 25.20
-------------------subtraction eliminates f, find h
5h = 29
h = 29/5
h = $5.80 for a hamburger
:
Find f using the 1st original equation, replace h with 5.80
4(5.8) + 2f = 27.10
23.20 + 2f = 27.10
2f = 27.10 - 23.20
2f = 3.90
f = 3.90/2
f = $1.95 for fries
:
:
Check solutions in the 2nd equation, replace h and f
3(5.80) + 4(1.95) =
17.40 + 7.80 = 25.20, confirms our solutions
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