How to find a proportion - SSAT Elementary Level Quantitative

Solve by cross multipling the two fractions.

Divide by on both sides.

To find a proportion, simply divide what you desire by the total.

In this problem the desired is the number of red marbles and the total is all of the marbels.

Thus,

To find a proportion, simply divide the desired amount by the total amount. We know our total by simply adding the marble amounts that compose it. Thus,

When solving a proportion, it is easiest to re-write it using fraction. So,

can be re-written as

Now, to solve this, we will cross multiply and divide.

To cross multiply, we will take the numerator of the first fraction and multiply it by the denominator of the second fraction. Then, we multiply the denominator of the first fraction by the numerator in the second, and set them equal to each other.

It might be easier to see an example.

Now, we divide to solve for x.

10% of 100 is calculated by multiplying .10 by 100.

13% of 100 is calculated by multiplying .13 by 100.

There are two ways to solve. First, you may see that the top numbers are related by multiplying by 2.

This means that the bottom numbers must also be related by multiplying by 2.

The missing number is therefore 8.

The other way to solve is to cross multiply:

Solve for by dividing 24 by 3:

The answer is again 8.

Cross multiply:

Solve for by dividing 135 by 9:

Cross multiply:

Solve for x by dividing 60 by 12:

of is calculated by multiplying . by .

of is calculated by multiplying by .

Adding Sofia's expenses shows that she spent a total of dollars. Subtracting this from the original amount of money she had gives the unspent portion: .

The ratio of the unspent portion to the original amount gives the fraction of the money that was not spent: .

To find of Brad's pay, multiply it by (since is the original number and is twice that). , which is the amount of the increase to Brad's pay. Add this increase to the original pay to get the new pay: per hour.

Multiply both sides by 3 to yield:

Multiply both sides by 8 to yield:

Therefore:

Therefore:

Set up a proportion of the new price to the old price to see how they relate.

of the original price

Subtract from to find the amount that was discounted.

Convert to a decimal by multiplying both the top and bottom of the fraction by , then convert to a percentage.

, which is equivalent to or

To find the length of the enlarged picture, we must set up a proportion:

cross multiply:

Divide both sides by 5:

In order to solve this problem, we need to make a ratio. Megan's teacher says she needs to have turned in 90% of her homework. First we need to change 90% into a fraction:

Using this information, we need to fill in the following ratio to find out how many assignments Megan needs to have turned in to be at 90% completion:

To solve this ratio, we need to cross multiply.

Now we have an equation to solve.

If we divide both sides by 100, we are left with our final answer.

Megan must have at least 45 assignments turned in if she wants to join the basketball team.