October 2009 SAT II - Math Level 2 - Page 3

jonnyboy1017 · 10-10-2009, 12:21 PM

backdgk-the fire alarm success one. im pretty sure its .997. because the probability of atleast one of them succeeding is 1 minus the probability of neither succeeding. so 1-(.08)(.04) equals .997

Randwulf · 10-10-2009, 12:22 PM

@bacdgk

The chance that one of the two goes off is higher than the chance that the more fickle one will go off. I'm not 100% sure this is right but I took the percentage chance that each alarm wouldn't go off and multiplied them (.08 * .04) and then subtracted that from 1. This gave me 99.7 or whatever, which was A.

I also got 6!

@jonnyboy1017

I'm pretty sure I said -3/root(13) like you did.

jonnyboy1017 · 10-10-2009, 12:22 PM

and ya i put 6! as well
and ya i got 109% too indian monster

Randwulf · 10-10-2009, 12:23 PM

@indianmonster

I got 109 as well. I did 11.6 * 1.03^25 and then divided that by 11.6 and subtracted 1.

bacdgk · 10-10-2009, 12:24 PM

Multiplying the probabilities is the odds that both will go off. The 1-(.08)(.04) makes sense now, I think I got that but decided against it for some reason :/

Randwulf · 10-10-2009, 12:25 PM

I'm feeling really good about my score now

Didn't get anything that we discussed in this thread wrong yet.

ESSENTIAL · 10-10-2009, 12:25 PM

@bacdgk the answer was 7.78%. It was a .3 percent increase or 16.1(1.003)^25 then you needed to find the percent of increase.

Monchichi · 10-10-2009, 12:25 PM

FUUU

"and ya i got 109% too"

htf did you guys get 109%, didn;t the question say 30% per year increase, I got some huuuge percent, so i guessed (wrong... lol)

Edit: OMFG .3 percent! I saw it and thought .3 chance = 30% Shiza. that would be incredibly unrealistic anyway.

jonnyboy1017 · 10-10-2009, 12:26 PM

bacdgk- i did that too for the percent population at first. but you have to do 11.6 x (1+.03) to the 25

Randwulf · 10-10-2009, 12:26 PM

I think it was 3% Monchichi

....ouch XD

bacdgk · 10-10-2009, 12:26 PM

It was .3% increase, I kept doing 1+.3 because I was used to big numbers when doing homework problems similar to this one :/

steelersngators · 10-10-2009, 12:27 PM

Was the second to last one eight and was the last one 3.8 or 4 something????

jonnyboy1017 · 10-10-2009, 12:27 PM

it said the pop. had a .3 percent increase (1.03) and just to check after the test, i multiplied 11.6 million times 1.03 25 times and got 109%

Randwulf · 10-10-2009, 12:29 PM

@jonny

thats what I did too but .3% is 1.003

Damn..

ESSENTIAL · 10-10-2009, 12:29 PM

a .3 percent increase is 1.003, a 3 percent increase is 1.03 and the question asked for the percent of increase not the percent of change so it was obvious that 109% was wrong. I did it as 1.03 at first too but then I realized that 109% increase couldnt be right