Teachers are buying treats. They bought 5 boxes of donuts for $12.75. How much would it cost them to buy 9 boxes of donuts?

Question

Help me with this question! This is urgent! i need it now.

Answer 1

Hi Gracie,

 

I'll urgently help you!

 

The best way to solve this is to think of proportions or ratios:  5 boxes is to $12.75 as 9 boxes is to X dollars.

 

This is written mathematically as 5/12.75 = 9/X

 

You solve by cross multiplying (top of one fraction times the bottom of the other):

 

5X = 9x12.75

 

Now you can multiply the numbers in the right side of the equation and then solve for X by dividing both sides by 5.

 

Have fun.

 

Dan

Answer 2

Try setting up a proportion! Let the donut boxes be the numerator and the dollars as the denominator.

5/$12.75 = 9/$x . Cross multiply to get $x for 9 boxes of donuts. You do this by multiplying so that if you were to trace the math, you end at the unknown value (think of it as a zig-zag pattern, multiplying diagonally first then dividing). So you start with 9 and multiply it with $12.75 which gives you 114.75 (9•12.75=114.75). You then divide by 5 so you have the amount it would cost. 114.75÷5= 22.95 so 9 boxes cost $22.95.

It should make sense: $22.95 is roughly twice as much as $12.75 so it should cost about about twice as much for 9 boxes as it does for 5.