time and work 2 sessions

Time and Work

2 Sessions

Welcome to Session 1

Agenda 2 Sessions

Time and Work

• Assumptions

•Man Days Concept

•Unit Work

•Work Units – Collaboration

•Alternative Working

•Efficiencies

•Negative Work

• Pipes & Cisterns

Session 1

Assumptions – T&W

Every person does the same amount of work!

Every day the same amount of work is done!

Man Days Concept

1. 10 men can do complete a work in 15 days. How many men are

required to complete the same work in 10 days?

2. 7 men working 8 hours a day can do a piece of work in 15 days.

How long will 21 men working 10 hrs a day take to finish the same

piece of work?

(1) 6 days (2) 9 days (3) 8 days (4) 4 days

3. 4 boys or 6 girls can do a piece of work in 18 days. How long will 2

boys and 9 girls take to complete the same piece of work?


4. 8 men and 15 women can do some work in 6 days. 15 men and 18

women can do the same work in 4 days. How long would 3 men and 9

women take to complete the same work?

(1) 6 days (2) 12 days (3) 24days (4) 18 days

5. Vijay and Sujay can complete a piece of work in 40 and 50 days

respectively. If they complete the work together and get paid Rs 1,800

then what is Vijay’s share?

(1) Rs 800 (2) Rs 1,000 (3) Rs 900 (4) Rs 850

6. Sita can do a piece of work in 20 days and Gita can do the same

work in 30 days. How long will they take to complete the work if they

are working together?


Alternate Day Working

7. A can do a piece of work in 20 days and B can do the same piece

of work in 30 days. If A and B work on alternate days starting from A,

In how many days would the work get completed.


8. A can do a piece of work in 8 days and B can do the same piece of

work in 10 days. If A and B work on alternate days starting from A, In

how many days would the work get completed.

(1) 4 (4/9) days (2) 8 (8/9) days (3) 8 (4/5) days (4) 9 days

9. A can do a piece of work in 8 days and B can do the same piece of

work in 10 days. If A and B work on alternate days starting from B, In

how many days would the work get completed.

(1) 4 (4/9) days (2) 8 (8/9) days (3) 8 (4/5) days (4) 9 days

Normal T&W questions

10. Praveen and Biju can do a piece work together in 24 days. They

start the work together and Praveen quits after 16 days. Biju

completes the remaining work in 20 days. How long would it take for

Praveen alone to complete the work?


11. Anu and Bhanu working together can finish a job in D days,

whereas if Anu is working alone she will take D+60 days to finish the

job, and if Bhanu is working alone she will take D+15 days to do the

same. What is the value of D?

(1) 75 (2) 60 (3) 30 (4) 45

12. Arun and Barun together can do a piece work in 24 days. Barun

and Karun together can do the same work in 40 days and Arun and

Karun take 30 days to complete the same work working together. How

long will Arun alone take to complete the work?


13. Alok and Bimal can do a piece of work together in 24 days. Bimal

and Chandra can do the same work together in 30 days. Alok started

the work alone and quit after 8 days. Then, Bimal took up the work

and worked for 18 days after which he had to quit. Finally Chandra

completed the remaining work alone in 30 days. How long would

Chandra have taken to complete the work alone?


14. Chetan and Chandan can complete a piece of work in 20 days

and 30 days respectively. Both work for 10 days and quit after which

Chintan completes the work in 8 more days. If they together get paid

Rs 3,600 find the share of Chintan?

(1) Rs 600 (2) Rs 1,000 (3) Rs 900 (4) Rs 800

Efficiency ConceptIf A can do a piece of work in 10 days and B can do the same work in 15

days , then Efficiency of A is greater than B !

If A can do a piece of work in 60 days at 100% efficiency.

Then,

at 50% efficiency he will take 120 days.

at 75% efficiency he will take 80 days

at 125% efficiency he will take 48 days

Efficiency ConceptA can do a piece of work in 20 days (say). And let’s say that you are given

efficiencies of 50%, 75%, 125% type of questions , then

You can assume that a can do Per Day, A can do say 4 units of work

at 50% efficiency he will do 2 units of work per day

at 75% efficiency he will take 3 units of work per day

at 125% efficiency he will take 5 units of work per day!

15. Akhil, Bhanu and Chandu can do a piece of work in 24, 30 and 40

days respectively. They start the work together and work for 5 days

after which Akhil quits the job and Bhanu develops a fever which

reduces his efficiency by a half. How many more days will be required

to complete the work?


16. Rita can do some work alone at 75% efficiency in 40 days. Mita

can do the same work in 40 days if she works at 125% efficiency. Find

the time taken to complete the work if both Rita and Mita work

together at 100% efficiency.

(1) 18.125 days (2) 18.25 days (3) 18.5 days (4) 18.75 days

17. 20 men can complete building a bridge in 15 days. However

due to an illness, 10% of the men lost 10% of their efficiency, 20%

men lost 20% of their efficiency and 30% men lost 30% of their

efficiency. How much time will the bridge take to be completed?

(1) 17.24 days (2) 17.34 days (3) 17.44 days (4) 17.54 days

Let each man do 10 units per day. 20 men, 200 units per day.

Total work required to be done : 3000 units

2 men – 90 % efficiency – 9 units per day = 18 units

4 men - 80 % efficiency - 8 units per day = 32 units

6 men - 70 % efficiency - 7 units per day = 42 units

8 men - 100% efficiency - 10 units per day = 80 units

Total units per day : 172 units , Hence 3000/172 = 17.44 days!

Pipes and Cisterns

Negative Work

18. Pipe A can fill a cistern in 20 mins and pipe B can fill the same

cistern in 30 mins. How long will it take to feel the cistern If both the

pipes are opened simultaneously?

(1) 15 mins (2) 25 mins (3) 12 mins (4) 10 mins

19. Tap A and tap B take 10 and 15 minutes respectively to fill a tank.

Both taps were opened together along with an emptying tap C. If the

Tank is full in 9 min, then how long will it take the emptying tap take to

empty the full Tank?

(1) 18 min (2) 25 min (3) 12 min (4) 16 min

20. A pipe can fill a tank in 10 hours. Because of the leak at the

bottom, it took 20 hours to fill the tank. In how many hours can the

leak empty a full tank?

(1) 20 hrs (2) 36hrs (3) 60 hrs (4) 30 hrs

21. Tap A can fill a tank in 20 mins and tap B can empty it in 30 mins.

Both were opened simultaneously and after some time tap B was

closed. If the tank was filled in 30 min, then what is the duration for

which tap B was open?

(1) 18 min (2) 25 min (3) 15 min (4) 20 min

22. A tank has 5 inlet pipes each of which can fill the tank in 6 hours

and 2 outlet pipes each of which can empty a full tank in 4 hours. If all

the pipes are open, how long does it take for the tank to be full?(CAT

1999)

(1) 90min (2) 120 min (3) 150 min (4) 180 min

23. A system of pipes is so designed that the capacity of the nth pipe is

equal the sum of the capacities of 1 to n-1 pipes. If P8 can fill a tank in

128 min, then how long will P11 take to fill the same tank?

(CAT 1999)

(1) 10 min (2) 4min (3) 16 min (4) 8 min

24. In a leather factory, bags and sandals are machine made.

Machine A can produce 20 bags every hour. It needs to be shut down

every 5 hours for 15 minutes. Machine B can produce 20 pairs of

sandals every hour. It needs to be shut down every 6 hours for 20

minutes. Find the number of products made in 7 days if the factory

works day and night.(count one pair of sandals as one product)?

(CAT 2004)

(1) 6360 (2) 6380 (3) 6400 (4) 6420

25. A chemical plant has four tanks (A, B, C and D), each containing

1000 litres of a chemical. The chemical is being pumped from one

tank to another as follows:

From A to B @ 20 litres/minute

From C to A @ 90 litres/minute

From A to D @ 10 litres/minute

From C to D @ 50 litres/minute

From B to C @ 100 litres/minute

From D to B @ 110 litres/minute

Which tank gets emptied first, and how long does it take (in minutes)

to get empty after pumping starts? (CAT 2005)

(1) A, 16.66 (2) C, 20 (3) D, 20 (4) D, 25

Thank You

time and work 2 sessions

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