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Time and speed Q from Tatamcgraw

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Time and speed Q from Tatamcgraw

by harry_x1 » Sat Jun 30, 2007 9:23 pm
1. Ram and shayam run a race of 2000 m. First , ram gives shayam a start of 200 m and beats him by 30 sec. Next ram gives shayam a lead of 3 min and gets beaten by 1000 meters. find the time in mins in which ram and shayam can run the race separately.

(a) 8, 10
(b) 4,5
(c) 5,9
(d) 6,9

2. A motorboat went downstream for 28 km and immidiately returned. It took the boat twice as long to make the return trip. If the speed of the river flow were twice as high, the trip downstram and back would take 672 mins. Find the speed of the boat in still water and the speed of the river flow.

(a) 9 km/h, 3 km/h
(b) 9 km/h, 6 km/h
(c) 8 km/h, 2 km/h
(d) 12 km/h, 3 km/h
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Re: Time and speed Q from Tatamcgraw

by gabriel » Sun Jul 01, 2007 12:37 am
harry_x1 wrote:1. Ram and shayam run a race of 2000 m. First , ram gives shayam a start of 200 m and beats him by 30 sec. Next ram gives shayam a lead of 3 min and gets beaten by 1000 meters. find the time in mins in which ram and shayam can run the race separately.

(a) 8, 10
(b) 4,5
(c) 5,9
(d) 6,9
.. let shyam run at the speed of x mts / sec .... now in the first case... ram gives shyam a start of 200m ... then, when ram runs 2000mts .. shyam runs 1800-30x mts ... so the ratio of their speed is 2000/(1800-30x)

for the second case .. shyam has a lead of 3 min that is 180x mts ... then, when ram runs a 1000 mts shyam runs 2000 - 18x mts so in this case the ration of their speed is 1000/(2000-180x) ...

equating the 2 ratios and solving for x we have x = 20/3 mts ....that is shyams speed is 20/3 mts ... so time taken to finish the race is 2000/(20/3) sec = 300 sec = 5 min .. now u can go on to solve for rams speed ... but it is not needed since there is only one option that gives shyams time taken as 5min ..option 2 .. so that shuld be the answer ...

btw ... are these gmat questions ... i myself havent seen such questions for gmat , if they are not gmat questions stop practising them... they wont be very helpful ....
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by harry_x1 » Sun Jul 01, 2007 12:45 am
you are right gabriel these are not gmat questions......
well i found that the questions on gmatprep software are much harder than what u encounter in OG....so i thought that it will be better to practise from a book which offers tougher questions....therfore m tryin to practise from tatamcgraw hill book on quatitave aptitude for prepatration of CAT admission test which is considered one of the toughest in India...
what is ur suggesstion ....as i m not particularly good at mathematics and my strong area is verbal only
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Re: Time and speed Q from Tatamcgraw

by gabriel » Sun Jul 01, 2007 12:49 am
harry_x1 wrote:2. A motorboat went downstream for 28 km and immidiately returned. It took the boat twice as long to make the return trip. If the speed of the river flow were twice as high, the trip downstram and back would take 672 mins. Find the speed of the boat in still water and the speed of the river flow.

(a) 9 km/h, 3 km/h
(b) 9 km/h, 6 km/h
(c) 8 km/h, 2 km/h
(d) 12 km/h, 3 km/h
.... let the speed of the boat be b and that of the stream be s ... so according to the first case ... 2( 28/(b+s)) = 28 /(b-s) .. solving we get b = 3s ...

now according to the second case we have ... 28/(b-2s)+28/(b+2s)= 672/60 hrs ... substituting b = 3s .. we have 28/s+28/5s = 672/60 .... solving for s we have s = 3km/hr ... now since b = 3s ... b = 9km/hr ... so the answer is a
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by gabriel » Sun Jul 01, 2007 1:52 am
harry_x1 wrote:you are right gabriel these are not gmat questions......
well i found that the questions on gmatprep software are much harder than what u encounter in OG....so i thought that it will be better to practise from a book which offers tougher questions....therfore m tryin to practise from tatamcgraw hill book on quatitave aptitude for prepatration of CAT admission test which is considered one of the toughest in India...
what is ur suggesstion ....as i m not particularly good at mathematics and my strong area is verbal only
... well cat questions are crazy tuff ,,, and u wont encounter such questions in gmat .. so u can stop practising cat questions ...

... if at all u want to practise tuff gmat problems then use the manhattangmat guides or kaplan , and also chk out different forums for quant problems u will get plenty of tuff problems ..

but bfor u do so make sure u have ur basics right ... once ur done with the basics start solving OG problems, make sure u understand the xpalnation to each problem and see if there are alternative approach to a particular problem ...

also since u r verbal is good ... make sure u score a 40 - 45 in verbal and that will take ur overall scaled score close to a 700 ... most colleges look at the overall score and even the top10-15 ask only for a 80 percentile clearing in both the sections ... so even if u have a low quant score a good verbal will take ur overall score to a good 700+ ...

.. also go thru other people statergies .. u will find them in most gmat related forum for BTG chk out " just beat the gmat " section ...
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by nishant kumar gupta » Tue Oct 14, 2014 5:47 am
let time taken by ram as t
speed of shyam becomes - 1800/t+0.5

from second equation
time taken by ram to complete 1000m is t/2 ( as for 2000m he takes t time)
hence speed of Shyam becomes = 2000/(t/2 + 3)
equate the two equation and you will get

t= 4min

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