Events & Promotions
|
|
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Nov 2211:00 AM IST
-01:00 PM IST
Do RC/MSR passages scare you? e-GMAT is conducting a masterclass to help you learn – Learn effective reading strategies Tackle difficult RC & MSR with confidence Excel in timed test environment- Nov 23
11:00 AM IST
-01:00 PM IST
Attend this free GMAT Algebra Webinar and learn how to master the most challenging Inequalities and Absolute Value problems with ease. 
Nov 2510:00 AM EST
-11:00 AM EST
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors.
10 Feb 2023, 18:52
Kudos
Bookmarks
Pmar2012
Bunuel IanStewart Pmar2012 KarishmaB : I like this methodology
However - i dont see why we are SUMMING UP the deviations.
We should be MULTIPLYING the deviations instead
Why ? Because it is 200 x 200 x 300
Thus the deviations are (0.5 %) x (0.5 %) x (0.3333 %)
Thoughts ?
10 Feb 2023, 21:24
Kudos
Bookmarks
jabhatta2
It's true that when we increase the dimensions by 0.5%, 0.5% and 0.3333...% we're really multiplying the volume by 1.005*1.005*1.00333333.... (you need to add 100% or 1 to each percentage in the part of your post I've highlighted to get the right percent increase). But when we have three very tiny percent increases, we can approximate the change just by adding them, because the compounding effect will be nearly zero. If you make an investment, say, and it increases in value by 1% each year for three years, you'll make just very slightly more than 3% (what you get by adding 1% + 1% + 1%), because there's almost no compounding with a percent change that small, unless you compound many, many times. I'm essentially just repeating what ThatDudeKnows' said above in his post. So as an approximation, it's fine just to add here. If the percent changes were large, however -- if we were increasing each dimension by 30%, say -- then there would be meaningful compounding, and adding would no longer give us a good estimate (the volume would increase in this case by roughly 120%, not by the 90% you'd get by adding 30 three times).
11 Feb 2023, 01:21
Kudos
Bookmarks
jabhatta2
Though Ian has already explained it, all I would like to say is try out the calculations to see it yourself too.
New Volume = LBH*(1 + 0.5%)(1 + 0.5%)(1 + 0.33%)
We need to get the value of the highlighted. Say the percentages are a, b and c for ease.
(1 + a)(1 + b)(1 + c) = 1 + a + b + c + ab + bc + ca + abc
Since a, b and c are very small values (0.5% etc), ab becomes much smaller .0025% which is much much smaller than a, b and c and hence can be ignored. Obviously abc is even smaller so can be ignored too.
New Volume = LBH* (1 + 0.5% + 0.5% + 0.33%) = LBH * (1 + 1.33%) = LBH + LBH * 1.33% approximately
So the change in volume is approximately LBH * 1.33%.
