SECTIONS: Third Section in the "Full Length SAT"
SCORE:13/16
TIME: 19 Minutes (20 Minutes Alloted)
( I was timing myself but i just finished whenever i finished.)
INCORRECT ANSWERS:
1. The most economical price among the following prices is :
10 oz. for 16 cents
2 oz. for 3 cents
4 oz. for 7 cents
20 oz. for 34 cents
8 oz. for 13 cents
I got this problem wrong because i unattentively divided ounces by cents, and not cents by ounces. It just didn't click that i needed to divide cents by ounces, but now i know.
I put 4 oz.for 7 cents, but the correct answer was 2 oz. foro 3 cents.
2. Each of the integers h, m, and n is divisible by 3. Which of the follwoing integers is always divisible by 9?
I. hm
II. h +m
III. h+m+n
I got this problem wrong because i first off didn't read it right and mistook the 9 for 3. But still, i took the approaach of filling in the answers and i thought that was a fool-proof method, but i am now even hesistant to use this method because i got this problem wrong.
I used 6,9,12 because all of those are divisible 3. This fulfills I, & III. Which is what i guessed.
The correct answer happened to be only I though.
You just have to represent h,m, & n with variable as such: 3a,3b,3c and then multiply and add blahblah
When should i substitute numbers in and when should i not?
3. A postal truck leaves its station and heads for Chicago, averaging 40 mph. An error in the mailing schedule is spotted and 24 minutes after the truck leaves, a car is sent to overtake the truck. If the car averages 50 mph, how long will it take to catch the postal truck?
I was dumb struck when i first began to solve this problem. I didn't go to far, because i had absolutely no clue on what to do. I knew what the d=r x t equation was but i couldn't put it in to effect here.
I understand that the distances are equal, and as they suggest in the book answers
50t=40 (t+.4)
but i don't get where the (t + .4) came from :[
BOOK: The Official SAT Study Guide: For the New SAT
SECTION: Second SAT Test, Math Section 1
SCORE: 16/20
TIME: 24 minutes out of 25 minutes
( I was timing myself but i just finished whenever i finished)
INCORRECT ANSWERS:
1. If 3/7 of n is 42 ,what is 5/7 of n?
Once again, a careless mistake.
2. What is the perimeter of the figure above?
24
25
28
30
36
I put down 24 but it was actually was thirty. My mistake was a matter of 6*4 or 6*5. Simply another careless mistake :/
3. There are 75 more women than men enrolled in Linden College. If there are n men enrolled, then, in terms of n, what percent of those enrolled are men?
n
A. ____ %
n + 75
n
B. _____ %
2n+75
n
C. ________ %
100(2n+75)
100n
D. ____ %
n+75
100n
E. ____ %
2n+75
I put down B. I picked two numbers once again 225 and 300, and it happened to work out with B. But the answer was actually E. Can you explain this to me?
4. 5.101001000100001000001...
The decimal number above consists of only 1's and 0's to the right of the decimal point. What is the total number of 0's between the 98th and the 101st 1 in this decimal point?
I know there must be some formula to be used because no one would actually count out something like that and be able to finish the section in the allotted time. Can you show me how to do this?
1 comment:
Opal,
Nice entry. You're really understanding the underlying issues in your work.
1. This is a careless mistake. No worries.
2. When should i substitute numbers in and when should i not?
This is a classic question. Substituting numbers is probably the correct way to do #2, but you can't always just substitute 1 set of numbers and assume that it will be correct for all situations.
On the SAT, you are trying to pick the right answer, or prove that 4/5 answers are wrong. When you do the algebra, you pick the right answer. When you plug in, you show that 4/5 are wrong. Just because an answer works with 2 numbers does not make it correct-- usually it has to work with all sets of those numbers.
Its especially tricky with the I II III question types, because they have the option none of the above, so you actually have to know why something is right.
Here's the rule: always use algebra if you can. Always. Its better to know the answer than guess it. For now, since you're still learning, do algebra on EVERYTHING-- it'll help you learn.
But if it looks like it is going to be faster to plug in numbers (esp if it multiple choice, not a I II III question), then plug in numbers. Plug them in in order to prove answer choices wrong. When you cant prove one wrong easily, make sure that you know why it could be right.
As well, when you plug in numers, always plug in really weird numbers like 0, 1, etc if possible-- that will test the limits of the equation.
3. Remember that minutes and hours are not equivalent. Speeds are expressed as miles per hour, but time can be expressed in mnutes. Thus the best way to fix this is to convert minutes to hours.
.4 hours is 24 minutes.
Thus, in this equation, you know that D= R*T
The distances are going to be the same
Thus, the equation for the distance that the police car goes is 50*t. And the equation for the distance that the truck goes is 40*(t+.4), since the truck had a head start of 24 minutes (.4hours).
Then you set them equal and get it.
Don't worry, you can always do lots and lots of rate problems to get them so that you're ready for that type of thing when the real test comes around. This stuff is easy when you practice it.
Good work!
Kapil
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