Sign in
Please select an account to continue using cracku.in
↓ →
A man rows 20 km upstream and back again to the starting point in 110 minutes. If the speed of the stream is 2 kmph, then the speed of rowing in still water is
Total time taken in journey = 110 mins = $$\dfrac{\ 11}{6}$$ hrs
Total time = $$\dfrac{\ 20}{V\ +\ 2}+\dfrac{\ 20}{V\ -2}$$ = $$\dfrac{\ 11}{6}$$ hrs
$$\dfrac{\ 11}{120}=\dfrac{\ 2V}{V^2-4}$$
$$11(V^2)-44=240(V)$$
$$11(V^2)-240(V)-44=0$$
Therefore, V = 22 kmph.