A tank can be filled by a tap A in 10 hours, whereas it can be emptied by tap B and tap C in 6 hours

M4maths Previous Puzzles

03 Aug 2012 Tank

A tank can be filled by a tap A in 10 hours, whereas it can be emptied by tap B and tap C in 6 hours and 12 hours one by one. If all the 3 taps work together, then total time taken for making a fully filled tank empty will be (in hours)

OPtion

1) 5
2) 4
3) 3
4) 2
5) 4.5
6) 3.5
7) 6.67
8) 7.5
9) 6.25
10) none of these

Solution

total tank filled by tap A in 1 hour = 1/10 part
similarly water drained by tap B in 1 hour = 1/6 part
and by tap C = 1/12 part
so total drained water in 1 hour = 1/6 + 1/12 - 1/10 = 3/20
so total time taken = 20/3 hours

Correct Option: 7 Best Solution (19)

somya kulshrestha   12 years AGO

ans.is 6.67
part emptied by pipes B and C respectively is 1/6 and 1/12 and part filled by pipe A is 1/10
when all taps are opened together
1/6+1/12-1/10 =18/120
thus time taken is 120/18=6.67

Like? Yes (10) | No   

chiru   12 years AGO

1/10-(1/6+1/12)
=-6.67(means empty)

Like? Yes (4) | No (1)  

IQBAL MEHDI   12 years AGO

6.67 ans.
tap A can be filled 1/10 of the tank in 1 hour
tap B and C can be emptied (1/6+1/12) 1/4 of the tank in 1 hour.
now, tap {A+(B+C)}'s 1 hour work=1/4-1/10=3/20
Since 3/20 of the tank is empty in 1 hour whenever three taps are working together
Hence,Tank will be emptied fully in 20/3 hours
That is in 6.67hours.

Like? Yes (4) | No (1)  

Devendra Marghade   12 years AGO

Total one hour capacity=1/10-1/6-1/12=-3/20
- sign shows that tank will be emptied at the rate of 3/20 per hour
So time require to empty full tank=20/3=6.67

Like? Yes (2) | No   

phani   12 years AGO

1/6+1/12-1/10=1/6.67
==>in6.67 hours it will be emptied

Like? Yes (2) | No   

ajitha   12 years AGO

A->1/10-->full
B->1/6-->empty
c->1/12-->empty
so,we can do
(1/10)-(1/6)-(1/12)=9/60=6.67

Like? Yes (2) | No   

ajay burnwal   12 years AGO

in 1hr tank will be filled or empty in
= 1/10-1/6-1/12.
=-3/20
so tank will be empty in= 20/3= 6.67hr

Like? Yes (3) | No (2)  

Chinmoy   12 years AGO

the tank will be empty in 1 hr(1/6+1/12)=1/4.
and the tank will be filled up in 1 hr by(1/10).
so the tank will be empty in 1 hr(1/4-1/10)=3/20
so tank will be empty by 20/3=6.67hr

Like? Yes (2) | No (1)  

abhisek kundu   12 years AGO

1/10-1/6-1/12=-3/20
20/3=6.67

Like? Yes (1) | No   

DANISH EQUBAL   12 years AGO

tap {A+(B+C)}'s 1 hour work=1/4-1/10=3/20
Since 3/20 of the tank is empty in 1 hour
Hence,Tank will be emptied in 20/3(6.67) hours.

Like? Yes (1) | No   

sandeep   12 years AGO

a's 1hr work 1/10 b's 1hr work 1/6 c's 1hr work 1/12
so when these 3 are worked together
1/10-(1/6+1/12) is -3/20 so total time is 20/3 i.e 6.67.Here - is used for emptying

Like? Yes (1) | No   

kishan vaghasiya   12 years AGO

for emptying the tank time taken by tap B and C together: 1/6+1/12=1/4. hence in 4 hrs tank can be emptied with both the taps.
now for filling it fully: 1/4-1/10=6/40 i.e. 40/6=6.67 hrs.

Like? Yes (1) | No   

satyaprakash vengala   12 years AGO

1/10-(1/6+1/12)=-3/20=6.67

Like? Yes (1) | No   

Manikandan   12 years AGO

L.C.M of 10,6,12=60
Total work=60
A's 1 hour work=6(60/10)
B's 1 hour work=10(60/6)
C's 1 hour work=5(60/12)
A&B&C's 1 hour work=(10+5)-6=9
The tank can be emptied in 60/9=6.6 which is the 7th option.

Like? Yes (1) | No   

vishnu   12 years AGO

1/10-(1/6+1/12)= -3/20.
so total time = -20/3.=6.6666666666666
or -6.67
- sign indicate tank will be empty.
So ans is option 7.

Like? Yes (1) | No   

moola srikanth   12 years AGO

1/10-(1/6+1/12)=-3/20=-6.67

Like? Yes (1) | No   

thadisetty srikanth   12 years AGO

1/10-(1/6+1/12)=-6.67

Like? Yes (1) | No   

Shiv Kumar   12 years AGO

(1/10)-(1/6+1/12)
=-(3/20) Negative means tank is empty

filled tank will be empty by 20/3 hours
=6.67

Like? Yes (1) | No   

mani   12 years AGO

time taken to empty the tank is
1/6 + 1/12 -1/12 , solving this we get 9/60.
taking reciporcal we get 60/9 which s 6.67

Like? Yes (1) | No