# HELP me with this math question??!!

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Ok dd11 is using Systematic Mathematics. Here is the question

A boys club raised money. They spent 3/5 of the money they raised on food, a total of \$17.10. How much money did they raise? How much money was left?

The answer is \$28.50 and \$11.40 left.

How does she write this equation? They have taught her to write things like this

Ex. 3 is what part of 12 would be the same as

3 = ____ x 12 or

what part of 30 is 1/8 would be the same as

_________ x 30 = 1/8

I can not for the life of me figure out how to make her understand how to write the equation for this word problem. Thanks for any help!!

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3/5 (money) = spent

Translation for 3/5 of money was spent on food.

Then put in numbers. Using words first is often very helpful in figuring out where numbers should go.

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Has she learned ratios? It is a very simple ratio problem to set up if she has.

3/5 of the money raised = \$17.10/total amt of money

Then it is simply a matter of cross multiplying/dividing.

Another explanation for the same process would be that if 3/5 = \$17.10 than dividing 17.10 by 3 is the equivalent of 1/5 and working from there.

HTH

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Well, we would bar graph this. :) Thanks to MM.

Total for food was 17.10, which was 3/5 of the money.

|____|____|____|____|____|

|______________|

17.10

|____|

5.70 (divided 17.10 by 3)

For that matter, 5.70 X 5 = 28.50

And, 5.70 + 5.70 = 11.40

Another way of doing this is the chart method, also taught in MM ...

1-5.70

2-11.40

3-17.10

4-22.80

5-28.50

Edit: I read your post again. I think that they want you to use this ....

x of y is z

"Of" means multiplication *

"Is" means equals =

3/5 * x = 17.10

Edited by ChrissySC
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Ok, thanks we have it. I just think the way they explain it is a little confusing.

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I would set it up like this:

3:5 = 17.10:n

(multiply outers and inners :), a silly jingle I learned way back when)

So, 3 x n = 5 x 17.10

3n = 85.50

n =28.50

So, the total amount is \$28.50. Then subtract the \$17.10 from the total (\$28.50) and get \$11.40.

When I took algebra many moons ago, I was taught to set those kinds of problems up as ratios and proportions. (Remember, a proportion is a statement that two ratios are equal.) It helped me tremendously to see how the numbers compared to each other that way. In other words, I would see this as 3 is to 5 as 17.10 is to what number (n).

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I would set it up like this:

3:5 = 17.10:n

(multiply outers and inners :), a silly jingle I learned way back when)

So, 3 x n = 5 x 17.10

3n = 85.50

n =28.50

So, the total amount is \$28.50. Then subtract the \$17.10 from the total (\$28.50) and get \$11.40.

When I took algebra many moons ago, I was taught to set those kinds of problems up as ratios and proportions. (Remember, a proportion is a statement that two ratios are equal.) It helped me tremendously to see how the numbers compared to each other that way. In other words, I would see this as 3 is to 5 as 17.10 is to what number (n).

Ooooh. I am so gonna steal this! Thanks!

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We would draw a rectangle to represent the total earned.

Then we would divide the rectangle into 5 pieces.

3 of those pieces total 17.50.

If you can figure out what one piece is you've got it made.

Generally from there they should see that 17.50 divided by 3 will give them the value for one of the pieces or 1/5.

Then the illustration makes it very easy to see that you add all the 1/5 pieces together to get the total. And you add the 2 pieces not colored in to get what was left.

I tell my kids when in doubt, draw a picture.

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