The following are TestTakers' suggestions for solving the problems on the October 16th, 2010 PSAT, Section 4 (a math section). Click "Read More" to view!
Showing posts with label arithmetic. Show all posts
Showing posts with label arithmetic. Show all posts
12/7/10
2010 PSAT - Saturday - Section 2 (Math)
The following are TestTakers' suggestions for solving the problems on the October 16th, 2010 PSAT, Section 2 (a math section). Click "Read More" to view!
4/26/10
Test 1 Section 7 - #11 (page 417)
If they're telling us she has a 2/5 probability of picking a brown towel, we can think of 2/5 as the ratio of brown towels to all the rest of the towels in her closet. Since they tell us she has 6 brown towels, we can set up a proportion to solve for the total towels:
Cross multiply to solve, and you'll see she has x = 15 total towels.
4/19/10
Test 7 Section 7 - #15 (page 788)
It would take us way too long to list all the numbers from 1-100 and check which are perfect squares. Luckily we don't have to. All we need to do is count all the ones that ARE, and then we know all the rest are NOT. To do so, let's just list squares of integers until they get bigger than 100:
12 = 1
22 = 4
32 = 9
42 = 16
52 = 25
62 = 36
72 = 49
82 = 64
92 = 81
102 = 100
112 = 121 (Oops, too big!)
There are 100 numbers between 1 and 100 (inclusive), and we just counted 10 of them that ARE perfect squares. That means 90 are not. Choice (E) is our answer.
12 = 1
22 = 4
32 = 9
42 = 16
52 = 25
62 = 36
72 = 49
82 = 64
92 = 81
102 = 100
There are 100 numbers between 1 and 100 (inclusive), and we just counted 10 of them that ARE perfect squares. That means 90 are not. Choice (E) is our answer.
3/17/10
Test 5 Section 4 - #15 (page 655)
This one is going to be a pain, because it's fractions. Blech.
Anyway, we've got 1/5 of a cup of OJ. which means we have 4/5 left to go to get to a full cup. We have to split that 4/5 up 3 ways, because the question tells us that the mix we use to fill the cup is split evenly in 3 parts. Forget about the other parts; we only care about the OJ.
To find how much more OJ we add, first convert 4/5 to 12/15. That's nice and divisible by 3. What's one third of 12/15? Because that's how much more OJ we add. We add 4/15 of a cup more OJ to our mix.
We started with 1/5 of a cup, which I'm going to convert to 3/15 now so we're adding with common denominators. We're adding 4/15 of a cup more OJ to our mix that started with 3/15 of a cup. We end up with 7/15 of a cup of OJ.
Anyway, we've got 1/5 of a cup of OJ. which means we have 4/5 left to go to get to a full cup. We have to split that 4/5 up 3 ways, because the question tells us that the mix we use to fill the cup is split evenly in 3 parts. Forget about the other parts; we only care about the OJ.
To find how much more OJ we add, first convert 4/5 to 12/15. That's nice and divisible by 3. What's one third of 12/15? Because that's how much more OJ we add. We add 4/15 of a cup more OJ to our mix.
We started with 1/5 of a cup, which I'm going to convert to 3/15 now so we're adding with common denominators. We're adding 4/15 of a cup more OJ to our mix that started with 3/15 of a cup. We end up with 7/15 of a cup of OJ.
11/23/09
Test 2 Section 2 - #4 (page 453)
This question is basically asking what percent of the total car sales April represents. We know there were 30 cars sold in April (from the given graph), but how many cars were sold total? Using the graph, that would be 20+18+22+30+48+42, which equals 180. So April had 30 of the 180 cars, which is equal to 1/6. Since a circle graph has 360 degrees, 1/6 of that would be 60 degrees, and the answer is (C).
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