Time SM doubts 2017-2019

Strictly all time study material doubts!!

Guys lets discuss all time sm material doubts here. Be it DI/LR/Quant/verbal. The shortest means to solve each and every question. A whatsap group can also be formed for the same, if suitable. So that our concepts our clear and we succesfully bell the cat.

hey ,did anybody finish the probability chapter from time study material??

N taps numbered from 1 to N are fitted to a tank.The rate at which the nth tap,for n=1,2,3....N fills the tank, equals the sum of the rates of all the taps numbered below it.If the sixth tap can fill it in 80 min find the time in which the ninth tap can fill it in minutes.

a. 10 b.5 c.20 d. 40

For Q#14, Is there any other approach apart from hit and trial?