Math Is Fun Forum

jxharmon

Member

Registered: 2007-01-08

Posts: 104

word problem

sally bought 3 candy bars and a pack of gum for $1.75; jake bought 2candy bars and four packs of gum for $2.00 find the cost of a candy bar and the cost of a pack of gum?

5 candy bars and 5 packs of gum = 3.75
5x +5y=3.75 and now I am stumped;
5x=-5y+375Help me please

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: word problem

You're on the right lines in that you need to combine the two equations to help you find out x and y, but you need to make sure that doing so will eliminate one of the variables.

Saying that x is the price of a candy bar and that y is the price of a pack of gum, we know that:

3x+y = 1.75
2x+4y = 2

We can multiply the first equation by 4 to give 12x+4y = 7.
Now we can subtract one equation from the other and eliminate y, rendering it solvable.

12x+4y - (2x+4y) = 7 - 2
10x = 5
x = 0.5

And from there, we can substitute the value of x into one of the original equations to find y.
y = 1.75-3*0.5 = (2-2*0.5)/4 = 0.25.

Therefore, the candy bar costs $0.50 and the pack of gum costs $0.25.

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Why did the vector cross the road?
It wanted to be normal.