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work rate

by maihuna » Tue Jul 28, 2009 11:22 am
GoodPuzzle:

A railway cutting 850m in length is to have a uniform depth of 4.5m ans its dimensions across the top and bottom are to be respectively 31.2m and 16.8m. If 450 tonnes are excavated on an avergae per day and 1 cubic meter weights 9/4 tonnes, how long the work require?

429 days
449 days
469 days
489 days
499 days
Charged up again to beat the beast :)
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by PussInBoots » Tue Jul 28, 2009 12:17 pm
459 days

4.5 * { (31.2 + 16.8) / 2 } * 850 m^3 * (9/4) tonn /M^3 would give the total amount of tonnes. Now just divide it by 450
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by prindaroy » Tue Jul 28, 2009 3:03 pm
I got 459 too, but apparently that's not one of the answers;

anyways here it is;

31.2+16.8/2 * 4.5 = area of trapezoid

24 * 4.5 = 108. So volume = 108 * 850

Weight = 108*850*9/4

Days to extract = (108*850*9/4)/450

= 459
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Re: work rate

by doclkk » Tue Jul 28, 2009 3:41 pm
maihuna wrote:GoodPuzzle:

A railway cutting 850m in length is to have a uniform depth of 4.5m ans its dimensions across the top and bottom are to be respectively 31.2m and 16.8m. If 450 tonnes are excavated on an avergae per day and 1 cubic meter weights 9/4 tonnes, how long the work require?

429 days
449 days
469 days
489 days
499 days
The numbers don't seem very gmatty ... ?
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by maihuna » Wed Jul 29, 2009 4:53 am
Yes 459 is correct one..
Its a prism question on base trapezoid. So found the volume using prism formulae...
Charged up again to beat the beast :)
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