Question

X and Y can do a piece of work in 20 days and 12 days respectively. X started the work alone and then after 4 days Y joined him till the completion of the work. How long did the work last?

6 days
10 days
20 days
15 days

Answer 1

Answer:

♠ The correct option is B.

Step-by-step explanation:

Let total work that has to be done is 120 units (common multiple of 20 and 12).  

In one day, X can do 6 units and Y can do 10 units of work. Thus, they both can do 16 units of work in a day.

In 4 days, X did (6 * 4) or 24 units of work.

After 4 days, work left to be done = 120 - 24 = 96.

Now, both X and Y work till the completion of work. They can do 16 units of work in one day. To complete at 16 units per day, 6 more days will be more required.

Total days = 4 + 6 = 10

Answer 2

Question :--- we have to find in how many day, work got completed....

Given :---- x can do the work in 20 days, y can do it in 12 days ..

Solution :------

LCM of 20 & 12 = 60

so, efficiency of X and Y = 3 and 5

Now it has been said that, X work for 4 days alone ..

so, in first 4 days, X completed = 4*3 = 12 unit of work .

Now, left work to be done = 60-12 = 48 unit ..

now this work is done by X and Y both .

they do work daily = 3+5 = 8 unit .

so, time they will take to complete rest work = 48/8 = 6 days ....

So, time to complete whole work = 6+4 = 10 days (B) (Ans)

(Hope this helps you )