# HCL aptitude questions

1. Three pipes A, B and C can fill a cistern in 12 hours. After working at it for 6 hours, C is closed and A and B can fill it in 10 hours more. How many hours will C alone take to fill the cistern?

• In 6 hours A, B and C would have filled 6 x $\frac{1}{12},$ = $\frac{1}{2},$of the cistern.

Remaining part is 1 – $\frac{1}{2},$ = $\frac{1}{2},$

which A and B have filled in 10 hours. → A and B can fill the whole cistern in 10 x $\frac{2}{1},$ = 20 hours.

• Its given that A, B and C can fill the tank in 12 hours.

So C can fill the cistern alone in $\frac{1}{12},$ – $\frac{1}{20},$ = $\frac{1}{30},$ = 30.

Hence C alone would take 30 hours to fill the tank.

1. Pipes M and N can fill a tank in 60 minutes and 30 minutes respectively. Pipe P drains 24 litres of water in a minute. If all of them are kept open when the tank is full, the tank gets emptied in 60 minutes. How much water can the tank hold?

• Let the drain pipe takes E minutes to empty the tank.

Now 1/60 + 1/30 – 1/E = -1/60.

The value on the Right Hand Side would be negative because full tank has been emptied.

• Solving this we get E = 15.

If the drain pipe can empty a tank in 15 minutes and its drainage rate is 24 litres per minute,

• the capacity will be 15 x 24 = 360 litres.

1. Raj purchases 40 apples for Rs.350 and sells 25 for Rs.350,then his gain percentage is?

• Change in quantity = 40 - 25 = 15

• Gain % = $\frac{15}{25}\times 100$

= $\frac{300}{5}$ = 60%.

1. A book was sold for Rs.38.50 with a profit 10%. If it were sold for Rs.35.70,there would have been a percentage of profit and loss of?

• CP = 100% , Profit = 10% $\Rightarrow$ SP = 110%

110% = 38.50

100% = $x$

$x\times 110 = 38.50\times 100$

$x$ = 35

CP = 35

• If it were sold for Rs.35.70 , we have a profit of .70 paise.

Profit % = $\frac{0.70}{35}\times 100$

= $\frac{70}{35}$ = 2%.

• Time=$\frac{Distance}{Relative speed}$
(Since opposit direction) Relative speed=$s_{1}+s_{2}$=7+5=12m/s
Time=$\frac{3600}{12}$=300 sec=5 min