Latest TCS Aptitude Question SOLUTION: A tank fills in the sequence of 10, 20, 40, 80.... (Means 10 litres in 1 hr, 20 litres in 2nd so on.). If at the 4th hour the tank is 1/4 full .When will it be full?

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A tank fills in the sequence of 10, 20, 40, 80.... (Means 10 litres in 1 hr, 20 litres in 2nd so on.). If at the 4th hour the tank is 1/4 full .When will it be full?

Asked In TCS Sri Reddy (10 years ago)

Solved Saraswathy Read Solution (15)

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Read Solution (15) :

Saraswathy  (10 years ago)

Sorry its 6

At the 4th hour, it ll fill 80 litres
80 litres is 1/4th of a tank...then the full tank can have 80 * 4 = 320 litres

Given series 10, 20 ,40 ,80, (ie) each litre is double of previous litres

so at the 5th hour tank filled ll be 80 * 2 = 160liters
At the 6th hr it ll fill the full tank (ie) 160 * 2 = 320

So the tank ll be full at 6th hr

Is this solution Helpfull? Yes (56) | No (9)  

Dhiren Paryani  (9 years ago)

10 litres-1hr
20 litres-2hrs
40 litres-3hrs
80 litres-4hrs
160litres-5hrs
320 litres-6hrs

Till 4th hour (10+20+40+80) litres of water is filled , tottal comes out to be 150 litres.. i.e 1/4 of total water..
X*1/4=150
x=600 litres(total capacity of the tank)

If by seeing above we can make out by 5 hours(10+20+40+80+160) 310 litres will be filled , we need 290 litres to fill up the whole tank.

In 6th hour 320 litres will be filled, we only need 290 out of that.

320 litres=60min
1litre=60/320 min
290litres=(60/320)*290 mins
Ans 5hrs 54mins

Is this solution Helpfull? Yes (23) | No (2)  

Devendra Marghade  (10 years ago)

5 hrs. 54 min.

In 4 hours tank filled(in liters)=10+20+40+80=150, which is 1/4 capacity of tank
So the full capacity=150*4=600 liters
The Sequence 10,20,40,80,... is a geometric series with a=10 & r=2
Sum of Geometric Series=a[(1-r^n)/(1-r)]=600, 2^n=61, So 5

Is this solution Helpfull? Yes (7) | No (5)  

ravindra reddy  (10 years ago)

At the 4th hour 1/4th of the tank is filled i.e, 150 litres makes 1/4 of tank(by summing 10+20+40+80)
Then 600 litres makes full tank.
Therefore 10,20,40,80,160,320=630 litres i.e, by 6th hour tank is full

Is this solution Helpfull? Yes (6) | No (2)  

ROHIT UPADHYAY  (10 years ago)

Ans---> after 6 hr

because in 4th hr tank is 1/4 full and fills 80 litres and timing is in sequence
so tank will be full when 80*4 = 320 liter water supply in tank..... so in 5th hr it is 160 liter and in 6th hr it is 320 liter

Is this solution Helpfull? Yes (5) | No (6)  

prem kumar  (9 years ago)

1/4 in 4th hour
1/2 in 5th hour;as here rate of water filling is doubled
1 in 6th hour

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pratikkmr01@gmail.com  (9 years ago)

6 hours 56 minutes..

Is this solution Helpfull? Yes (2) | No (4)  

Niveditha Ravichandran  (9 years ago)

1 hr - 10 lit
2 - 20
3 - 40
4 - 80

4th hour - tank is 1/4 full
so 10+20+40+80 = 150 litres -> 1/4 full

remaining litres (3/4) for the tank to get full --> 150*3=450 litres

5th hour - 160 lit
6 - 320 lit

total - 480 lit

but for the tank to get full required is 450 litres - 30 litres extra
so, b/w 5th to 6th hour- 160 lit is filled in 1 hour(60 min)
130 lit is filled in 48 mins

sol: 5 hour 48 min

Is this solution Helpfull? Yes (2) | No (1)  

Saraswathy  (10 years ago)

the tank fills 10 litres per hour
At the 4th hour, it ll fill 40 litres
40 litres is 1/4th of a tank...then the full tank can have 40 * 4 = 160litres

160 litres if filled in 16 hrs

so the tank ll be full at 16th hr

Is this solution Helpfull? Yes (1) | No (3)  

arsalan  (9 years ago)

at 1st hour 10
at 2nd hour 20=10*2
at 3rd hour 40=20*2
so at each next hour it double
it is given the question that
at 4th hour 1/4
so at 5th hour 1/4*2=1/2
and at 6th hour 1/2*2=1 (i.e. full)
so after 6 hour the tank will be full.

Is this solution Helpfull? Yes (1) | No   

apoorva  (9 years ago)

for every hr tank is doubled.
so in 4th hr-1/4
5th hr-1/4+1/4=1/2
6th hr-1/2+1/2=1
for 6 hrs the tank will be filled.

Is this solution Helpfull? Yes (1) | No   

Soheli Bhaduri  (9 years ago)

Let x be the volume of the tank.
x/4=80,x=320 l
At 5th hr it is 160l full,at 6th hour it is 320l full
So,at 6th hr it is full.

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karthikeyan  (9 years ago)

5th hour 160
6th hour 320
time taken 1hour54mints
total time taken 5hour 54mints

Is this solution Helpfull? Yes | No (1)  

manisha kumari  (9 years ago)

tank is 1/4 full, no of 2 in 1/4 is 1/2*2=2.add 4th hour +2=6hr

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rahul kumar  (9 years ago)

at 6 hour.

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