# Speed problem. Please help with steps.

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• Oct 19th 2012, 09:42 AM
hisajesh
Speed problem. Please help with steps.
A locomotive engine without a train can go 24 km an hour and its speed is diminished by a quantity, which varies as the square root of the number of wagons attached. With 4 wagons its speed is 20 km per hour. FInd the greatest number of wagons with which the engine can move.
• Oct 19th 2012, 11:15 AM
MaxJasper
Re: Speed problem. Please help with steps.
n<144
• Oct 22nd 2012, 03:06 PM
HallsofIvy
Re: Speed problem. Please help with steps.
f(0)= 24 and f(4)= 20. Its speed has been "diminished" by 4 and that is $k\sqrt{4}= 2k= 4$ so that k= 2. $24- k\sqrt{n}= 24- 2\sqrt{n}= 0$ gives $\sqrt{n}= 12$ which gives MaxJasper's answer.
• Oct 23rd 2012, 10:11 AM
hisajesh
Re: Speed problem. Please help with steps.
Thank you both Halls ofIvy and MaxJasper!