Question

An engine without wagon can go at the rate of 24 kmph and its speed diminishes by a quantity which varies as the square root of the
number of wagons attached. With four wagons its speed 20 kmph. The greatest number of wagons with which the wagon can move is :

• A. 143
• B. 144
• C. 145
• D. 122
• E. 123

Answer 1

The correct option is A

143

Decrease in speed = 24 - 20 = 4

$4=k\sqrt{4}\Rightarrow k=2$

Now, for the speed to decrease to zero

$24=k\sqrt{x},$ where x is the number of wagons which

will stop the engine

X= 144

The greatest number of wagons with which the wagon can move is 143