PSAT Math : Proportion / Ratio / Rate
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Example Questions
Example Question #11 : How To Find Proportion
A factory makes six widgets in a batch that takes 24 minutes to complete. How long does it take to make 57 widgets?
3 hours
3 hours, 5 minutes
4 hours
3 hours, 45 minutes
3 hours, 30 minutes
4 hours
We have here a basic ratio:
6/24 = 57/x
Solving for x, we get: 6x = 24 * 57; 6x = 1368; x = 228
Now, we must be very careful here, however. Is 228 an even multiple of 24? 228/24 = 9.5. That means that we would have to do 9.5 batches. The question indicates that these are batched in groups of 6; therefore, we have to run 10 batches to get our amount. That would be 240 minutes or 4 hours.
Example Question #11 : How To Find Proportion
Kendall can run 26 miles in 4 hours and 20 minutes. At this rate how long would it take him to run 100 miles?
16 hours and 40 minutes
18 hours and 35 minutes
15 hours and 50 minutes
12 hours and 20 minutes
10 hours and 55 minutes
16 hours and 40 minutes
Set up a proportion and conver 4 hours and 20 minutes into just minutes for now,
so 26/260 = 100/X
Solve for X = 1000 minutes
1000/60 = 16 hours and 40 minutes
Example Question #12 : How To Find Proportion
A recipe calls for a ratio of 
We can set up a ratio of 
Example Question #11 : How To Find Proportion
To ship a package, the postal service charges 
The weight will be 150 grams + (1.15 – 0.55)/0.05 * 50g.
You need to subtract first 150 grams cost from the total cost and divide by the price per unit to determine how many units. Next, multiply units by weight per unit and add to the original first 150 grams.
150 + 600 = 750 grams
This is the maximum weight that can be sent at that price; the minimum weight that could be charged this price would be 701 grams. Hence a package weighing 750 grams will be charged $1.15.
Example Question #17 : How To Find Proportion
Six is to thirteen-and-a-half as seventeen is to what?
None of the other answers are correct.
Let us express this as an algebraic expression:
We can cross multiply:
Example Question #1631 : Psat Mathematics
Out of 85 students in a certain class, 42 own a laptop and 54 own an mp3 player. If 5 students don't own either, what fraction of the students own both a laptop and an mp3 player?
1/8
19/80
1/10
16/85
7/40
16/85
Once you subtract the 5 students that don't own either, there are 80 students left.
There's 96 total students when you add the number that own an mp3 and the number that own a laptop, meaning 16 own both.
Recall that the fraction will be number of students who have both laptop and mp3 divided by the total students in the class.
Example Question #1 : How To Express A Fraction As A Ratio
express 7/8 as a ratio
0.875
not possible to express as a ratio
8:7
1.15
7:8
7:8
a ratio that comes from a fraction is the numerator: denominator
7/8 = 7:8
Example Question #71 : Arithmetic
1 meter contains 100 centimeters.
Find the ratio of 1 meter and 40 centimeters to 1 meter:
12:5
2:3
3:2
9:6
7:5
7:5
1m 40cm = 140cm. 1m = 100cm. So the ratio is 140cm:100cm. This can be put as a fraction 140/100 and then reduced to 14/10 and further to 7/5. This, in turn, can be rewritten as a ratio as 7:5.
Example Question #54 : Proportion / Ratio / Rate
When television remotes are shipped from a certain factory, 1 out of every 200 is defective. What is the ratio of defective to nondefective remotes?
1:199
199:1
200:1
1:200
1:199
One remote is defective for every 199 non-defective remotes.
Example Question #55 : Proportion / Ratio / Rate
On a desk, there are 
Begin by making your life easier: presume that there are 
By cross-multiplying you get:
Solving for 
(Many students will likely see this fact without doing the algebra, however. The numbers are rather simple.)
Now, this means that our desk has on it:
Therefore, you have 
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