SOLUTION: Suppose that Kristin ate two McDonald hamburgers and drank one meduim Coke for a total of 770 calories. Kristins friend Jack ate three hamburgers and drank 2 Cokes for a total of

Algebra ->  Customizable Word Problem Solvers  -> Age -> SOLUTION: Suppose that Kristin ate two McDonald hamburgers and drank one meduim Coke for a total of 770 calories. Kristins friend Jack ate three hamburgers and drank 2 Cokes for a total of       Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 673733: Suppose that Kristin ate two McDonald hamburgers and drank one meduim Coke for a total of 770 calories. Kristins friend Jack ate three hamburgers and drank 2 Cokes for a total of 1260 calories. How many calories are in a McDonalds hamburgers? How many calories are in a meduim coke?
Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
let x = munber of hamburgers
let y = number of medium cokes.
your equations become:
2x + y = 770
3x + 2y = 1260
solve for y in the first equation to get y = 770 - 2x
substitute for y in the second equation to get:
3x + 2*(770 - 2x) = 1260
simplify to get:
3x + 1540 - 4x = 1260
combine like terms and subtract 1540 from both sides of the equation go get:
-4x = 1260 - 1540 which becomes:
-x = -280
multiply both sides by -1 to get:
x = 280
the number of calories in a mcdonald's hamburger is 280.
replace x with 280 in either equation and solve for y.
we'll use the equation of:
2x + y = 770
replace x with 280 and you get:
560 + y = 770
subtract 560 from both sides to get:
y = 770 - 560 which becomes:
y = 210
the number of calories in a medium code is 210.
you get:
x = 280
y = 210
x = number of calories in a hamburger.
y = number of calories in a medium coke.
2 hamburgers and 1 medium coke is 2 * 280 + 1 * 210 which is equal to 770 calories.
3 hamburgers and 2 medium cokes is 3 * 280 + 2 * 210 which is equal to 840 + 420 which is equal to 1260 calories.
numbers check out so the answer is good.