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504.Grass in a lawn grows equally thick and at a uniformrate. It takes 24 days for 70 cows and 60 days for30 cows to eat the whole of the grass. How manycows are needed to eat the grass in 96 days?(a) 18(c) 24(e) of these(b) 20(d) 36 |
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Answer» 24 days 70 cows ==total work done=24*70=1680 60 days 30 cows === total work done= 60*30= 1800 Now see here that total work done must be the same but there is a difference . that difference corresponds to the increasing grass/day ie. work done by grass work done by grass =1800-1680 =120 (this work is done in (60-24=36 days). work done by grass per day =120/36= 10/3 now work done by grass in 24 days= (10/3)*24=80 actual work = 1680 -80 = 1600 now work done by grass for 96 days = (10/3)*96== 320 total work required to be done = 1600 + 320 = 1920 cows required = 1920/96 == 20 |
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