momo555 Posted June 30, 2012 Report Share Posted June 30, 2012 Hello all, I was wondering if you could share how to solve these questions. This is from official OAT website A tank can be filled by a pipe in a 30 minutes and emptied by another pipe in 50 minutes. How many minutes will it take to fill the tank if both pipes are open? Answer is 75 min ( what's the easiest method to get to this answer? ) Optometry school applicants decreased by 25% during 4 year period. During the same time, the number of first-year opening in optometry school increased by 12%. If the ratio of applicants to first year openings had been 3 to 1, then which of the following would be the approximate ratio at the end of 4 year period? Answer is 2:1 (how????) When each of the sides of a squqre is increased by 1 yard, the area of the new square is 53 square yards more than that of the original square. what is the length of the sides of the original square? Answer is 26 (how????) Calculate variance of following set of numbers (3,6,9,18) The answer is 27.5 (how do you calculate variance in hand?) Link to comment Share on other sites More sharing options...

cantcatchme Posted July 6, 2012 Report Share Posted July 6, 2012 These are answers that I figured out when I read your post - I think they're correct (I got the right answer anyways) #1 (minutes passed)/(minutes required to fill or empty the tank) = how much tank is filled so, (minutes passed)/30 minutes = amount of tank full (minutes passed)/(-50 minutes) = amount of tank empty The amount of tank full/empty are as fractions Let's say t= minutes passed t/30 - t/50 = 1 it equals 1 because the tank is full solve for t #2 A1 = Applicants at year 1 A4 = Applicants at year 4 O1 = Optometry student opening at year 1 O4 = Optometry student opening at year 4 0.75 A1 = A4 1.12 O1 = O4 A1:O1 = 3:1 So, A4:O4 = 0.75(3) : (1.12)(1) = 2:1 *there is a calculator given to you so this will be easy to calculate using that .. the actual ratio is 2.0089:1, but you can also see that 2.25:1.12 is approximately 2:1* #3 x=original length in yards So in the original square x^2 = Area With the increase of 1 yard, new length is x+1 So, (x+1)^2 = new area In the question it says the area increased by 53 yards so, x^2+53 is the new area (x+1)^2 = x^2 + 53 Solve for x #4 Use the variance formula to calculate it.. you have a basic calculator It could be time consuming, but you can calculate in your head quickly (it would be faster than clicking on a calculator) I can't teach you that, you just have to practice and recognize multiples easily Good luck Link to comment Share on other sites More sharing options...

momo555 Posted July 7, 2012 Author Report Share Posted July 7, 2012 Thank you!!!! Link to comment Share on other sites More sharing options...

KCA Posted July 30, 2012 Report Share Posted July 30, 2012 Question 1 could also been done this way Let X be the size of the pool Rate of actual pool filling=rate in-rate out= x/30 - x50=2x/150=x/75 And well... There you have it... Already... But if you want the whole thing... Fill volume=rate*time Let t be time... We want to fill the whole pool, thus... x=x/75 * t T=75 Link to comment Share on other sites More sharing options...

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