Answer: 16 days

Explanation:
(A + B + C)’s 1 day work = 1/18
In 6 days (A + B + C) do 6/18 of work, i.e. 1/3 of work
Balance work = 1 – 1/3 = 3-1/3 = 2/3
A’s one day work = 1/72
(B + C)’s 1 day work = 1/18 – 1/72 = 3/72 = 1/24
(B + C) will take 2/3 × 24 = 16 days

Answer: 24 min

Explanation:
Let it take as x hours for the vessel to be emptied.
x(1/8 – 1/12) = 1
x(3 – 2)/24 = 1
x = 24 mins

Answer: 337.5, 270,225

Explanation:
In 1 ½ hours, i.e. 90 min, A throws 8 × 90 = 720 shovels of mud
B throws 10 × 90 = 900 shovels of mud
C throws 12 × 90 = 1080 shovels of mud
Total shovels of mud thrown in 90 min = 720 + 900 + 1080 = 2700
Time that A alone require = 2700/8 = 337.5 min
Time that B alone requires 2700/10 = 270 min.
Time that C alone requires = 2700/12 = 225 min.

Answer: 12 hrs

Explanation:
In one hour (A + B + C) can fill 1/6 of the tank
In 2 hours ( A + B + C) can fill 2/6 = 1/3 of the tank
Remaining part of the tank to be filled = 1 – 1/3 = 2/3 of the tank
Time taken by (A+B) to fill 2/3 of tank = 8 hours
(A+B) can fill the whole tank in 8 × 3/2 = 12 hours
C alone can fill the tank in [1/6 – 1/12 = 1/12]
12 hours

Answer: 7 1/5

Explanation:
A’s 4 day’s work = 1/3
A’s 1 day’s work = 1/12
B’s 3 day’s work 1/6
B’s 1 day’s work = 1/18
(A+B)’s 1 day work = 1/12 + 1/18 = 5/36
A and B together will complete the work in 36/6 days
= 7.2 days

Answer: 2*50/71

Explanation:
A alone takes 32/3 days; B alone takes 48/5 days and C alone takes 64/11 days.
Working together (A + B + C) can complete (3/32 + 5/48 + 11/64) of work in 1 day, i.e.
(18 + 20 + 33)/192 = 71/192
They will take 192/71, i.e. 2 50/71 days 

Answer: 14 days

Explanation:
A’s one day work = 1/32 and B’s one day work = 1/40
(A+B)’s one day work = 1/32 + 1/40 = 5+4/160 = 9/160
(A+B)’s 10 days work = 9 × 10 / 160 = 9/16
Remaining work = 1 – 9/16 = 7/16
A will finish the work in 7/16 / 1/32 = 14 days.

Answer: 14 sec

Explanation:
In 4 seconds, the car reduce the distance by 100 cm. hence in 12 seconds, the distance is reduced to 200 cm. in the 13th and 14th second, the cars come forward by 100 cm each and hence collide. So the gap of 500 cm is reduced in 14 seconds.

Answer: 28 min

Explanation:
In one minute the worm climbs (3 – 2), i.e. 1 ft of the burrow.
In 27 min, it will climb 27 ft and in the next 1 minute it will climb 3 ft. at the end of 28th min, as it reaches the top of the well, it will not slip down.
It takes the worm 28 minutes to reach the top

Answer: 30

Explanation:
 In 1 minute the first tap will fill 1/10 of the cistern and the other tap will empty 1/15 of the cistern.
Let the cistern be filled in X minutes
X(1/10 – 1/15) = 1 i.e. X(3 – 2 / 30) =1
X = 30 min
Hence, the cistern will be full in 30 minutes.