Math Problem

Test Preparation SAT Preparation
1

<p>Each student in a group of 30 students studies German, Italian, or both. The total number of students studying German is 3 more than the total number of students studying Italian. If the number of students that study both subjects is the same as the number of students that study exactly one subject, how many students in the group study only Italian?
A) 6
B) 9
C) 15
D) 21
E) 24</p>

<p>This one showed up at the end of the section and I spent the remaining 5 minutes I had left to no avail ._....</p>

2

<p>So, let's look at what we know:</p>

<p>We know that x # students study Italian, and x + 3 # students study German. If we take the 15 students studying both out of the equation [as the # students studying both = the # students studying one], we know that 15 students take only one of them. Therefore, if 2x+3 = 15, x = 6.</p>

<p>6 students take only Italian.</p>

<p>[TBH this took me a few minutes just to set up, so I'm not absolutely positive about the answer]</p>

3

<p>Real easy.</p>

<p>You know italians are i and germans are 3 + i.</p>

<p>Now simply plug in.</p>

<p>Take 6.</p>

<p>i= 6
3+i = 9
Both = 15 </p>

<p>6+9=15
15=15</p>

<p>So that works.</p>

4

<p>Ahh, I get it. Thanks a lot.
Also, one more problem I had trouble with.</p>

<p>At a certain hospital, 89 children were born in the month of June. If more children were born on the fifteenth of June than on any other day in June, what is the least number of children that could have been born on the fifteenth of June?</p>

<p>This is a grid-in. It was pretty confusing for me, and I only got it out of sheer luck/rapid plugging in.</p>

<p>Anyone know a more systematic way?</p>

5

<p>The answer is 6. </p>

<p>The algebraic way takes quite a while, here goes.</p>

<p>First list what you know. </p>

<p>G=3+I
G-B+I-B+B=30 AKA G+I-B=30
B=G+I-2B AKA 3B= 3+2I</p>

<p>Now, lets take it all under 1 variable. Lets do I.</p>

<p>G= 3+I
B= 3+2I/3
I= 3+I - 3 = I</p>

<p>G+I-B = 30
3+I + I - (3+2I) / 3 = 6+4I/3
6+4I/3 = 30
I = 21 .</p>

<p>Plug it into 3B= 3+2I
42+3 = 3B
B= 15
21 = number of ppl who take italian, and 15 ppl take both.
21-15 = 6.
I= 6. </p>

<p>there</p>

6

<p>For your second QUestion, the key is knowing how many days there are in june. </p>

<p>We have 30 days in june.</p>

<p>89 children were born in 30 days. </p>

<p>for a day to have the MOST children born, every other day has to have the least. </p>

<p>89/30 , we get 2.9 , which isnt possible. but thats close to 3, and it doesnt have to be for all 30 days.
3x29= 87 . Thats only 2 short of 89, but then that would make all the days equal.
3X28= 84</p>

<p>oo, thats pretty close. we still have 2 days left. So we put the LEAST for one day. Which is 1.</p>

<p>84+1 = 85.</p>

<p>1 day left.</p>

<p>89-85=4. </p>

<p>4?</p>

7

<p>I don't understand how something like the June question can be included in an SAT Math test, as it seems to require outside knowledge.</p>

8

<p>^That one was from a QAS, but I agree, it's pretty arbitrary of ETS to include a question like that, which assumed you knew how many days were in June.</p>

9

<p>hm,the baby born problem was not really arbitrary, seems like it tests your knowledge of 'remainder' ... but yeah alot of people had trouble with this back in may lol.. </p>

<p>2nd Q was kinda logic based too, common sense in a way lol.
89 childrens, 30 days.
2 children per day, that's 60 childrens, 29 children left, use 28 children and put into each day, 1 children left, make that stand out,it's 4. lol that was weird language..</p>

10

<p>This question is completely legitimate. Just because 90% of h.s students in this nation still have trouble with the calendar , which is pretty much "universal", doesn't make the question any more or less unfair. Now, if there was a question that involves converting meters to kilometers, should you cry simply because you didn't have a ruler? Its high school guys, these things should be 2nd nature.</p>

11

<p>^The metric system is pretty familiar to MOST high school students, but ETS still likes to provide the measurements. The days is a little arbitrary, not everyone knows the amount of days in each month. I only knew that 30 days was in June because it was recently June, lol.</p>

12

<p>But the test is supposed to cover mathematics, not general knowledge.</p>

13

<p>Math isn't "general knowledge" ? Btw Shiomi, over 50% of H.S students in this nation have trouble with the metric system. I wouldn't be so quick to say "most" students know it well.</p>

14

<p>i dont really know the metric system lol...
yeah i know that 1k=1000m, but cm and milli gets a lil confusing,thers some others.. lol..</p>

15

<p>^But you don't live in the US though right?
You pass...</p>

16

<p>Same here. Im working on it- ETS is probably going to fire prob dealing wit the metrics in oct. Watch out dawgs.</p>

17

<p>^The metric problems are usually part of the first couple of ones given, isn't it?
And they usually give like the units already. Plus, usually dimensional analysis wouid suffice to solve it - at least I think so...
I've only gone through about 5-6 QAS and the problems are usually the straight forward conversion ones, except for this one weird ruler trick problem, but that was more of a word problem. </p>

<p>But yeah, the October SAT is going to be jammin, I'll see you ladies there.</p>

18

<p>i live in the us territories... so thats US.
the metric system is so annoying lol. the last time i saw it was probably 2 yrs ago from chem class... oh i hat ethat class.</p>

19

<p>That test is gonna get rocked. Ya dig.</p>

20

<p>What is it like 20 days?
Psh, I bought a watch, pencil sharpener, and top of the line pack of pencils.
All from Wal-Mart, cost me about 10 bucks.
Ren are you chinese?</p>