This is merely a subtype of Time n Work problems. and can be solved using our good ol’ STD table Method.

# Case 1: Women finish entire job

4 men and 6 women can complete a work in 8 days, while 3 men and 7 women can complete it in 10 days. In how many days will 10 women complete it?

Suppose 1 man can pour 1 bucketful of water in the tank in 1 minute.

If 6 men work together, they pour 6 buckets in a tank in 1 minute.

In short, you multiply the speed with number of person.

Our usual table

1 Man | 1 Woman | 4 men & 6 women | 3 men & 7 women | |

Speed | m | w | 4m+6w | 3m+7w |

Time | 8 | 10 | ||

distance |

Distance covered in each column is same.

So compare last two columns

Distance = distance

Speed x time = speed x time

(4m+6w)*8=(3m+7w)*10

Solve this equation and you get m=11w

Replace this value of w in last column

1 Man | 1 Woman | 4 men & 6 women | 3 men & 7 women | |

Speed | m | w | 4m+6w | 3(11w)+7w |

Time | 8 | 10 | ||

distance |

3(11w)+7w

=33w+7w

=40w

1 Man | 1 Woman | 4 men & 6 women | 3 men & 7 women | |

Speed | m | w | 4m+6w | 40w |

Time | 8 | 10 | ||

distance | 40w x 10= 400w |

So the total work is

Speed x time = distance

40w x 10= 400w

If 10 women work together, they’ve to cover 400w kms. Make a new column, run STD formula

1 Man | 1 Woman | 4 men & 6 women | 3 men & 7 women | 10 women | |

Speed | m | w | 4m+6w | 40w | 10w |

Time | 8 | 10 | ?? | ||

distance | 40w x 10= 400w | 400w |

10w x time =400w

Time =400w/ 10w=40days.

Answer: If 10 women work together, it’ll take 40 days to finish the job.

# Case 2: Women to finish remaining job

12 men can complete a piece of work in 4 days, while 15 women can complete the same work in 4 days. 6 men start working on the job and after working for 2 days, all of them stopped working. How many women should be put on the job to complete the remaining work, if it is to be completed in 3 days?

12 Man | 15 Woman | |

Speed | 12m | 15w |

Time | 4 | 4 |

distance |

Distance covered in both column is same so compare them

Speed x time = speed x time

12m x 4= 15w x 4

4m=5w

M=(5/4)w

The question is asking about number of women in the end, so better convert everything in terms of women.

**Given: ** 6 men start working on the job and after working for 2 days, all of them stopped working

Make a new column.

12 Man | 15 Woman | 6men | |

Speed | 12m | 15w | 6x (5/4)w |

Time | 4 | 4 | 2 |

distance | 60w | 6x (5/4)w x2=15w |

As you can see, I’ve applied STD formula in last two columns to find distance simultaneously.

Remaining work=60w minus 15w=45w

Required: we want to finish this work in 3 days.

**Asked:** *How many women should be put on the job to complete the remaining work, if it is to be completed in 3 days?*

Make a new column. Suppose we need “F” number of women so speed = f x w = Fw.

12 Man | 15 Woman | 6men | Find women | |

Speed | 12m | 15w | 6x (5/4)w | Fw |

Time | 4 | 4 | 2 | 3 |

Distance | 60w | 15w | 45w |

Time limit is given to us: complete remaining work in three days. So t=3 for last column.

Run STD on last column

Fw x 3 =45w

F=45w /3w

F=15

Answer : 15 women required.

**Important**: Remaining work is to be completed in 3 days. So t=3

If they had asked “total work is to be completed in 3 days”, we’ll need to take t=1, because those men already worked for 2 days to only 1 day left to complete the job (2+1=3 days)

# Case: Child labour

Twelve children take sixteen days to complete a work which can be completed by eight adults in twelve days. Sixteen adults started working and after three days ten adults left and four children joined them. How many days will they take to complete the remaining work?

12 kids | 8 men | |

Speed | 12k | 8m |

Time | 16 | 12 |

Distance |

Since work done in both columns is same

Speed x time = speed x time

12k x 16= 8m x 12

K=(1/2)m

Concentrate on middle column (8 men) run STD table on it. You get distance = 8m x 12 =96m

So total distance to be covered is 48m

Given: Sixteen adults started working and after three days ….

Means 16 men worked for 3 days.

12 kids | 8 men | 16 men | |

Speed | 12k | 8m | 16m |

Time | 16 | 12 | 3 |

Distance | 8m x 12=96m | 16m x 3=48m |

We’ve run STD on last column and got that 16 men covered 48m kms.

So remaining work is 96m minus 48m=48m

Given: after three days ten adults left and four children joined them

So now men left =16 minus 10 =6 men and 4 kids joins them so speed is 6m+4k

Make a new column

12 kids | 8 men | 16 men | Men & kids | |

Speed | 12k | 8m | 16m | 6m+4k |

Time | 16 | 12 | 3 | ?? |

Distance | 96m | 48m | 48m |

Run STD on last column

(6m+4k) x time =48m

But We already calculated that K=(1/2)m

Apply it in above equation{6m+4(1/2)m} x time =48m

{6m+2m} x time = 48m

8m x time = 48m

Time =48m /8m

Time=6 days.

beautifully explained, aptitude seems to be very easy by your explainations sir

concepts made very easily, aptitude seems to very easy by your explaination sir

i dnt knw wats ur future plans , but if u stand for election .. whole youth of india will vote for u !!! mrunal long live …

i dnt knw wats ur future plan , but if u stand for election whole youth of this country will vote for u . mrunal long live

Plz solve dis by ur method: Q) A,B,C can do a piece of work in 12,15,20 days respectively..If A is working all the time, B and C are working alternatively,then in how many days work wil be done?

ans- 120/17

as per the technique,

A B C A+(B/2)+(C/2)

speed A B C A+(B/2)+(C/2)

Time 12 15 20 ??

Distance 12A 15B 20C 12A

12A=15B=20C

Now, Time= 12A/[A+(B/2)+(C/2)] _____since time= dist./speed

By solving above equation u’ll get 120/17 ans.

Whats the answer??

I am getting 7 days..I may be wrong..I am known to do silly mistakes!!! :)

u r right …………ans is 7 days

Plz also solve other models in work,time,wages like A can do 25 percent work,b does 1/6th work……so on

THANK U!!!! so much for giving a such wonderful tricks to solve the problem…………………..THANK u sooo much……….

Mr. A finish a worked on 12 days. when Mr. B finished this work on 15 days and Mr. C on 20 days separately. but after 2days A left the work and B left the work before 2days finished the work. How many day worked will be finished?

Plz solve this question ?

hello Megha!

A – 12

B – 15

C – 20

in question they say that after 2 days A left

now we will find how much work they have done in 2 days

2*( 1/12 + 1/15 + 1/20 ) = 2/5 it means they have completed 2/5 work .now remaining work

is 1-2/5 = 3/5

let form here own-word that they (B and C) finish the work in D days .

D* 1/20 + (D-2)* 1/15 = 3/5

form here D comes ——————– 44/7 days.

final answer is 2 + 44/7 = 58/7 days .

please replay if i am wrong .

Ur right mohit kumar….I solve it in std technique.I got same answer…:-)

Please solve

5 women and 3 men done any work in 10 days. 4 women and 4 men done this work in 3 days. How many days that 10 women take to done this work?

Mr. A finish a worked on 12 days. when Mr. B finished this work on 15 days and Mr. C on 20 days separately. but after 2days A left the work and B left the work before 2days finished the work. How many day worked will be finished?

sol : (more simple)

let they complete the work in x days then,

x/20+(x-2)/15+2/12=1;

=> 58/7 days (ans)

x/20= C’s total work

(x-2)/15= B’s total work

2/12 = A’s total work

(you can do such questions with approach)

Mr. A finish a worked on 12 days. when Mr. B finished this work on 15 days and Mr. C on 20 days separately. but after 2days A left the work and B left the work before 2days finished the work. How many day worked will be finished?

sol : (more simple)

let they complete the work in x days then,

x/20+(x-2)/15+2/12=1;

=> 58/7 days (ans)

x/20= C’s total work

(x-2)/15= B’s total work

2/12 = A’s total work

(you can do such questions with approach)

Hello friends I am from vocational Background but working really hard from SSC preparation. Please hint me on the solving following time and work problems.

1. If 5 men or 8 women can do a piece of work in 12 days, how many days will be taken by 2 men and 4 women to do the same work

2. 15 women can do 1/2 work in 20 days. In how many days will 20 women do the full work?

3. A and B can be a piece of work in 10 days and C and A in 20 days. C alone can do the work in `

4.Two taps can separately fill a cistern in 6 and 7 minutes respectively. If the taps are opened turn by turn each for a minute, find the time taken by them to fill the cistern.

1st sol: since work is same apply speed*time-distance , so 5m*12w=8w*12,solve for 1 w=5/8m asks:2m+4w=days? Put 1w=5/8m n sol ve tht is 9/2m nw 5m do in 12 days n 9/2 m will do in 40/3 d ..its min whts urs

i have solved 2nd

ans is 120?

nice stuff admin .thank u..

Hai, i have doubt on following question, please help me to solve quickly,

A alone can complete a work in 16 days and B alone can do in 12 days. Starting with A, they work on alternate days. The total work will be completed in how many days?

Pls help me solve this question using above STD method

A alone can complete work in 16 days and B alone in 12 days.Starting with A ,they work on alternate days.The total work will be complted in how many days?

20 women can do a job in 20 days. after each day, a woman is replaced by a man is twice as efficient as a women on which day does the job gets completed??? anyone

well ans-10 days..becz if each woman replaced by a man-tht mean 20 men,but efficiency is high time will be less.so half time in my opinion

Respected sir, I was unable to solve following 2 problems from Time and work. It looks complicated to me. Plz,help.

problem 1- B can do a job in 6 hrs.B and C can do it in 4 hrs, and A,B,C in 2*(2/3)hrs.In how many hrs can A and B do it? option (a)3*(3/4) (b)3*(3/7) (c)2*(3/7) (d)4*(3/7)

problem 2- A and B can do a piece of work in 12 days.A and C together work twice as much as B, A and B together work thrice as much as C. In what time could each do it separately?

can any one solve the question by using STD table method

urgent coz i got some confusion-”

A can lay railway track between two given stations in 16 days and B can do the same job in 12 days. With help of C, they did the job in 4 days only. Then, C alone can do the job in:

Question : 6 men can complete the electric fitting in a building in 7 days .how many days will it take 21 men to do the job?

mob : 9799422423

plz reply……………………..fast

how we calculate

Remaining work=60w minus 15w=45w

in 2nd Que explain above by mrunal sir.

easy method is take out efficiency

let men no be =x

and womwnen = y

efficiency of 4m and 6w together = 100/8 = 12.5%

efficiency of 3m and 7w together = 100/10 = 10 %

so,

4x+6y=12.5 – 1

3x+7y= 10 – 2

solving one and two u get y = 1/4% (efficiency of women per day)

for 10 women multiply by 10 = 10/4%

so number of days would be 100/10/4 = 40 days

Thanks sir becoz of only u now m able to solve questions VERY easily…and concepts also get cleared. Thanku…

Mrunal sir,how to solve this problem?

Two persons A and B together can do a work in 10 days.The same work can be finished in 18 days if A works alone for 12 days and B works alone for 6 days.find the time required for each of them to finish the work if they work alone?

really u r einstein’s incarnation

Thank you, you teach and explain in a way that is so simple yet very effective. I wish you all the best. Thanks again.

mrunal sir or any1 plz solv dis from rajesh verma..a certain persons cn dig a trench 200 m long ,20 m deep ,100 m broad.thn the same no of persons dig another trench 40 m broad 30 m deep in 60 days..find length of 2nd trench..explain step by step ..if possible unitary method..

ji i tried….but i didnt get…. if u got answer…pls explain me

Thanks a lot Mrunal.ORG :)

Twelve men can complete a work in 8 days. Three days after they stated the work, 3 more men joined them. In how many days will all of them together complete the remaining work?

plz here me to solve the above problem in a simple way Twelve men can complete a work in 8 days. Three days after they stated the work, 3 more men joined them. In how many days will all of them together complete the remaining work?

SOLUTION :-. APPLY STD TABLE

MEN MEN MEN

S 12 12 12 + 3 = 15

T 8 3 60/15 = 4 DAYS

D 12X8 = 96 36 96 – 36 = 60 ANS. 4 DAYS

SOLUTION IS NOT SHOWING PROPERLY

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A,B and C can do a piece of work in 10, 12 and 15 days respectively. A leaves 5 days before the completion of the work and B leaves 2 days after A. the whole work lasts for

if 5 men finish a work in 12days, how many days will it take 8 men to finish the same work?

In how many ways 4 letters can be placed in 4 envelops such that none of them are going to the right envelop?

Use time*efficncy = work

Since work is same ,

12*5=k*8…….find out k…

A, B and C can finish a piece of work in 30, 40 and 60 days resoectively. 10 days after they started to work together B leaves. 4 days after B left, A leaves and C completes the remaining work. How many days C had worked altogether

4 men or 6women or 10 children can paint ahouse in 5 days the painting is given to a couple and 5 sons they finish the job in

A can do a work in 10 days & B can do that work in 15 days. A & B both work together for 5 days. Rest of work is completed by C. They get rs 1500 for the work. How much salary B & C can get?

Find out the answer please

There are 17 apples in a box. In how many ways we can distribute it to 3 people such that first person gets at least 1 , second gets at least 2and third gets at least 3..

Hi Vishnu,

Step 1 -> give 1 apple to 1st person , 2 apples to 2nd person and 3 apples to 3rd person.

now you are left with 11 apples.

each apple out of 11 can be distributed in 3 ways.

so total no of ways -> 3 power 11

Hi Salman

But up to some part seems correct..

Total no of ways not 3^11. , but it is 13C2..i think so..if wrong please excuse me

11C3 ways=165 ways

sorry ji 165 wrong