GMAT Math : Calculating ratio and proportion
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Example Questions
Example Question #11 : Ratio & Proportions
A fathom is a unit of underwater depth equal to six feet.
Express two miles in fathoms.
Multiply 2 miles by 5,280 feet per mile, then divide by 6 feet per fathom:
Example Question #12 : Ratio & Proportions
A furlong is a measure of length used in horse racing. Eight furlongs are equal to one mile.
Express 20 furlongs in feet.
Divide 20 furlongs by 8 furlongs per mile, then multiply by 5,280 feet per mile.
Example Question #12 : Ratio & Proportions
127 people signed up for a subscription service. 45 signed up for weekly deliveries, 34 for monthly deliveries, and the rest for annual deliveries. What is the ratio of weekly subscribers to annual subscribers?
Let's first find the number of annual subscribers:
The ratio of weekly subscribers to annual subscribers is therefore 
Example Question #14 : Ratio & Proportions
A clothing store is having a sales for the holiday season. They mark down all items by 
We start by finding the value of the mark down:
Therefore, the mark down is 43.8% or 0.438, which means that the new price of the suit is:
Example Question #15 : Ratio & Proportions
Noah and Lilly both work for Company ABC. Lilly earns 
What was Lilly's salary in 2013?
We start by finding Lilly's salary in 2012:
$60,000 x 1.20 = $60,000 + $12,000 = $72,000
Then we account for the annual 10% increase to find Lilly's salary in 2013:
$72,000 x 1.10 = $72,000 + $7,200 = $79,200
So Lilly's salary in 2013 was $79,200.
Example Question #16 : Ratio & Proportions
Company 
If the amount of soda sold per dollar is the same for each company, what is 
Since the amount of soda per dollar is the same for each company, we can equate the 2 ratios
And solve
Example Question #17 : Ratio & Proportions
Ms. Lopez earned $236.25 after working 15 hours last week. At this rate, how much will she have earned if she works 25 hours?
The first thing we must do is set up our equation. We do this by writing our earnings to hours worked ratio:
where 
We can then solve this equation for 
Then,
Example Question #13 : Ratio & Proportions
George just finished the first week of his new job. He calculated that if he works 50 hours in two weeks, his biweekly paycheck will be $812.50. If he has worked a total of 27 hours so far, how much additional money must he earn in order to reach $812.50?
$373.75
$621.00
$438.75
$432.75
$373.75
He has worked 27 hours out of the 50 hours calculated. As such, we are asked how much he will earn after working the remaining 23 hours.
We can first find his hourly pay and then calculate his earnings for 23 hours.
where 
He earns $16.25 an hour
We can now calculate how much he earns for the remaining 23 hours:
So, George needs $373.75.
Example Question #11 : Proportion / Ratio / Rate
A small company's workforce consists of store employees, store managers, and corporate managers in the ratio 10:3:1. How many employees are either corporate managers or store managers if the company has a total of 
Let 
Therefore, the number of employees who are either store managers or corporate managers is 
Example Question #19 : Ratio & Proportions
A scale model of the newest Mars rover has a wheel radius of 
Setting up a proportion here is the way to go. To make our proportion even easier to solve, set it up in such a way that your unknown (antennae length for the actual rover) is in the numerator. Recall that in a proportion, we want to have similar parts together. In this case, we will keep the wheel radii on the left and the antennae lengths on the right.
By leaving our unknown on top, we can solve this in one fell swoop. Simply multiply both sides by 
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