single room double room

[blover]

i figured out efficient way to do this

1400*15 + 420 *20 = 420 X

X= 50 +20 => 70 ans

[theRealGMATstrategies]

allright,

this problem is fairly simple. However, as always, the GMAT tricksters confuse the wording to delay you finding the right solution. So, the best way with problems of this kind is always figure out how much a person does in one hour. In this case, you can easily establish that one person does 4 single rooms in one hour and 3 double rooms in one hour. Next, in seven hours one person can do 28 single rooms and 21 double rooms. The last step is to set up a ratio 1p/28=x/1400 and 1p/21=y/420. Add the values for x and y to get the total number of people. There are ways to de-confuse this problem through simple drawing, but unfortunately I can not show that --- although if you are interested ---- I could show - just email me. Also, remember, that there are different ways to solve this problem. However, also remember, that the GMAT tricksters rely on you to use algebra because they know that under time pressure if you use algebra, you are likely to make a mistake, so whenever you can try to avoid algebra without sacrificing time. I solved this problem in 2 minutes 19 seconds. This is a bit too long, as you need to keep your timing at 2 minutes per problem. If you are interested in talking about timing strategies, etc, email me, and we will talk....

[theRealGMATstrategies]

One more thing. I think this problem is a wonderful example of what I call the "Break-Layer" GMAT method. What this means is that GMAT tests relatively easy math concepts. In this particular problem, the concept being tested is the ratio. However, if you notice the test makes you use three different ratios in order to solve this problem. So, by piling up the concept of ratio and feeding you a confusing word content, the GMAT tricksters are making you use valuable time.

[rkwagle]

Imo B

[blover]

earlier i use that approach

15minutes -- 1 room
420 minutes --- X room
x=28 rooms

28 rooms --1 man
1400 rooms --x man
x=50men




20 min --1 room
420min --x rooms
x=21rooms


21rooms---1man
420rooms--- -xmen
x=20men

so 50men plus 20 men =70men