December 2nd, 2009
Is There A Less Stupid Way To Do This Gre Math Question?
MBA University, by mba ranking.at the rate of F/3 feet per M minutes, how many feet can a bicycle travel in S seconds.
The answer is fs/180m. Christ, there has gotta be an easier way than plugging in every multiple choice answer to see if its correct.
Or is that the only alternative. I’d appreciate it.
Think of it a step at a time.
1. We start with the rate: F/3 feet per M minutes.
2. (F/3)feet/M minutes. (same thing, just written differently).
3. (F/3)Feet/60M seonds. (because there are 60 seconds per minute).
4. F Feet / 180M seconds. (Combining the bottoms).
5. That’s the rate…Mutilply by S seconds because you’re give that the bike went S seconds. F Feet / 180 M seconds * S seconds = FS Feet / 180M.
or….
1. Time * Rate. S seconds * (F/3) feet/ M minutes,
2, (FS Seconds / 3) feet / M minutes.
3. (FS Seconds / 3) feet/ M 60 seconds
4. FS/180m feet
Ok…that will get you there, but how do you do it quickly? The best way is to practice lots of rate conversions until you are really good at the. Do probelms involving 10 men painting houses in so many days, and the like. Practice, practice, practice.
That said, there is a real fast way of doing it, if you can think it out. If something is traveling so many feet per minute, it will be going a lot less in one second. Hmmm..1/60th in fact. One 60th of 1/3 is 1/180. Since you don’t know how many seconds or minutes the bike ever traveled, you need the S and the M in the anwser somewhere. The M stays on the bottom where it started, and the S is on the top, becasue you know there are so many seconds PER minute (s/m). You can do that in less than a minute. WIth Multiple choice it’s often faster NOT to do the math.
F / 3 ft/minute
= (F / 3) ft/minute x 1 minute / (60 seconds)
= (F x 1) / (3 x 60) ft/s
= F / 180 ft/s
Distance travelled in S seconds
= Speed x time
= F / 180 (ft/seconds) x S seconds
= FS/180 ft
Please check foot and metre confusion
F/3 feet per M ?
what does that mean?
Here is a way to solve it directly (without having to plug in all answers):
The speed of the bicycle is (F/3)/M = F/3M feet/minute
However, you want the speed in feet/second, so multiply the above by 1/60 minute/second to get:
(F/3M)*(1/60) (feet/minute)*(minute/second) =
F/180M feet/second
Now since you want the distance in feet traveled in S seconds, multiply by S seconds to get:
(F/180M)*S (feet/second)*second = FS/180M feet
Note that on the GRE since you want to maximize points/minute, you will want to consider which of the following is the best alternative for each type of problem:
1) solve directly
2) plug in answers
3) guess relatively intelligently and go on
If during you practicing you find a particular type of problem to be very troublesome do not hesitate to pick choice 3 and go on to easier problems.
Good luck!
You are given the speed and time…is it that difficult to get distance ???
Speed = F/3 feet in M min =F/3 feet in 60M seconds
= F/(180M) feet/s
Time = S seconds
So distance = Speed*Time =FS/(180M)
First, figure out rate in seconds:
(F/3 feet per M minutes) x (1 minute/ 60 seconds) = (F/3M)/60 feet per seconds = F/180M feet per seconds
Second, multiply rate and time to yield distance (i.e. distance traveled):
(F/180M feet per seconds) x (S seconds) = FS/180M feet
Hope that helps! Good luck!