Aptitude - Time and Work - Discussion

Can we solve such questions by LCM method? Please help.

A    1x
-- = --- (RATIO OF TIME)
B    3x

And difference is given 60 days.

3x-1x=60.

1x = 30 days for A.
3x = 90 days for B.

I don't remember but I think I have posted the another method up above long time before.

Time ratio between A and B is 1:3.

A/B = 1/3------ (1).

B takes thrice the time taken by A.

A-B = 60 from A = B+60--- (2).

BY substituting (2) in (1).

Then get time taken by B to finish work in 90 days.

From (1) you get time taken by A to finish work in 30 days.

A's 1 day work is = 1/30.

B's 1 day work is = 1/90.

(A+B) 1 day's work is = (1/30+1/90) = 2/45.

Then time taken by the A and B working together is 45/2.

We can solve this question easily.

A:B = 1:3.

Difference is 60.

Hence ratio becomes:

A:B = 30:90 = 1:3.

Here we can see diff is 60.

So our answer will be 90*30/90+30 = 270/12.

= 90/4 = 45/2 = 22+1/2.

So much confusing answer given. This is basically ratio problem.

60 days less means you have to take ratio of time and solve the problem. A is thrice as better as B means. B takes thrice time compared to A.

i.e Ratio of time taken by A/B = 1/3.

If B takes x days then A takes x-60 days time to complete the work.

i.e Ratio of time taken by A/B = x-60/x.

Therefore 1/3 = x-60/x.

Solve to get x = 90 therefore B takes 90 days and A takes 30 days.

Daily Work of A = 1/30.

Daily Work of B = 1/90.

Adding work of A and B.

Daily work of A and B is 4/90.

So time taken for both A and B to complete the work is 90/4 = 221/2 days!

Simple as that!

A is thrice good as B.

So, ratio of work done is 3:1 and A taken 60 days less as compare to B.

Let time taken by B is x so time taken by A is x-60.

So 3:1::x:x-60.

3x-180 = x. So 2x = 180 and x = 90.

Time taken by B = 90 days so time taken By A is 30 days.

A's one day work = 1/30 and B's one day work is 1/90.

Total work done by both A and B in one day = 1/30+1/90.

= 3+1/90 = 4/90 = 2/45 = 22.5 days.

Hi friend.

This is one of easiest problem.

Here given that the ratio of time taken of A and B to complete one work in individually is 1:3.

So let us take A can do this work in X days and that of B is 3X days.

According to conditions B took 60 days more than A.

3X-X = 60.

2*X = 60.

X = 30.

So time taken by B is 3*30 = 90 days and by A is 30 days.

When A&B together do this work. The required time is:

= 1/(1/30+1/90).

= 1/((3+1)/90).

= 45/2 days.

Please tell me how is the difference of time is 60 days?

Hi @Sagar.

It is mentioned in the question.

A is thrice as good as B. So A = 3x and B = x.

A is 60 greater than B. So 3x-x = 60.

2x = 60.

x = 30.

A = 90 and B = 30.

1/90+1/30 = 45/2.

Answer: 22 1/2.