A is thrice as fast as B and is therefore able to finish a work in 40 ...
Given,
Ratio of time taken by A and B = 1 : 3
∴ B takes 3 days to finish a unit work while A takes 1 day to finish the same work
The difference of time is 2 days
Given,
Difference of time is 40 days
∴ Time taken by B to complete the work = [(3/2) × 40] = 60 days
∴ A takes 20 days to finish a work
⇒ Work in 1 day by A = 1/20
⇒ Work in 1 day by B = 1/60
⇒ Work in 1 day by (A+B) = [(1/20) + (1/60)] = 4/60
∴ A and B will take days to complete the work = 15 days
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A is thrice as fast as B and is therefore able to finish a work in 40 ...
Given:
A is thrice as fast as B
A finishes the work in 40 days less than B
To find:
Time taken by A and B working together
Solution:
Let the time taken by B to finish the work be x days.
Then, the time taken by A to finish the same work would be x/3 days.
According to the question, A finishes the work in 40 days less than B.
So, we can write the following equation:
x/3 = x - 40
Solving for x, we get:
x = 60
Therefore, B takes 60 days to finish the work.
And A takes 20 days to finish the same work. (Since A is thrice as fast as B)
Now, let's find the time taken by A and B working together.
Let the total work be 1 unit.
Then, in 1 day, B can do 1/60th of the work.
And in 1 day, A can do 1/20th of the work.
So, in 1 day, working together, A and B can do:
1/60 + 1/20 = 1/30th of the work
Therefore, the time taken by A and B working together to finish the work would be:
1 / (1/30) = 30 days
Hence, the correct answer is option (D) 15 days.