Time and Work

1) A and B can complete a work in 16 and 32 days respectively. A works alone for 10 days, then B joined and completed the work. How many days A and B were working together?

Answer Is: (B) 4 days

Explanation:

A = 16 days
B = 32 days
A alone worked for 10 days.
Work done by A in 10 days
=> ( 1 / 16 * 10)
=> ( 5 / 8 )
Remaining work = ( 1 -( 5 / 8))
= ( 8 - 5 ) / 8
= 3 / 8
A + B one day work
=> ( 1 /16 + 1 / 32)
=>( ( 2 + 1) / 32)
=> ( 3 / 32)
Now (3 / 32) work is done by A and B in one day
So ( 3 / 8) work will be done by A and B in ( 32 / 3) * (3 / 8)
=> 32 / 8
=> 4 days.

2) A pipe can empty a cistern in 20 minutes. Find the time in which 3/4 part of the cistern will be emptied.

Answer Is: (D) 15 min

Explanation:

We have 1/20 part of the cistern emptied in 1 minute
=> 3/4 of the cistern will be emptied in 20 x 3/4 = 15 minutes.

3) Mr. Win can complete 40 % of the work in 12 days. Calculate the total number of days he takes to complete the work ?

Answer Is: (D) 30 days

Explanation:

40 % of the work is completed in 12 days
No of days taken to complete 100% of work is=> (100/40) x 12 = 30 days

4) Mr. A and Mr. B can do a piece of work in 8 and 12 days respectively. If both of them work together, in how many days the work will get completed ?

Answer Is: (C) 24 / 5 days

Explanation:

A 's 1 day work = 1/8
B's 1 day work = 1/12
When both work together, 1 day's work = (1/8) + (1/12) = (3+2) / 24 = 5 / 24
Number of days to complete the work will be 24 / 5 days

5) A and B can complete the work in 20 and 36 days respectively. A works for the first 5 days and then quits. How many days B has to work to complete the work ?

Answer Is: (D) 27 days

Explanation:

A 's 1 day work = 1/20 A's 5 day work = 5/20 = 1/4
B has to do the remaining 3/4 of the work B will take 36 x (3/4) days = 27 days

6) X,Y,Z complete a given work in 12 , 42 and 28 days respectively. If all three of them work together, in how many days the work will get completed ?

Answer Is: (D) 7 days

Explanation:

X's 1 day work = 1/12
Y's 1 day work = 1/42
Z's 1 day work = 1/28
All three are working together
X+Y+Z 's1 day work = (1/12) + (1/42) + (1/28)
[L C M of 12 , 42 , 28 = 84]
= (7 + 2 + 3) / 84 = 12 / 84
X+Y+Z 's 1 day work = 1/7
X+Y+Z will take 7 days to finish the work
Answer is 7

7) One fill pipe A is 3 times faster than second fill pipe B and takes 32 minutes less than the fill pipe B. When will the cistern be full if both pipes are opened together?

Answer Is: (A) 12 min

Explanation:

Let pipe A takes x minutes to fill cistern
The, pipe B takes 3x minutes to fill the cistern
Given, A takes 32 minutes less than B
=> Time taken by pipe A - Time taken by pipe B = 32 minutes
=> 3x - x = 32 minutes
=> x = 16 mins
=> Time taken by pipe A to fill cistern = 16 mins
Time taken by pipe B to fill cistern= 3x = 3 * 16 = 48 mins
So Time taken by both the pipe to fill cistern
= (48 x 16) / (48 + 16) minutes
= 12 minutes

8) Hemal can complete a work in 8 days, what percentage of the work would be completed in 2 days ?

Answer Is: (B) 0.25

Explanation:

Lets considers 8 days as 100 %, the work gets done So 4 days is 50 % where half of the work is done So when Arun has worked for 2 days, then => (2/8) x 100 = 100/4 = 25 %

9) 36 men can complete a work in 18 days. In how many days will 54 men can complete the same work?

Answer Is: (B) 12

Explanation:

Less men means more days ( Inverse proportion) 54 : 36 :: 18 : x => x = (36 x 18) / 54 = 36 / 3 = 12 Required number of days = 12, with 54 people working on it

10) 16 men can complete the job in 8 days, then in how many days the work will get complete if employ 8 more people.

Answer Is: (C) 16/3 days

Explanation:

16 men can complete in 8 days
1 man can do in (8 x 16) days
8 more people, now the total number of people = 8 + 16 = 24
24 men will take (8 x 16)/24 = 16/3 days

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