Given:
A takes 10 days more than B to finish a task.
They both do the work together for 5 days and finish part of the work.
Concept used:
The time is taken by A to complete the work = a
The time is taken by B to complete the work = b
The amount of work done = L.C.M of (a and b) = c
Efficiency of A = ac
Efficiency of B = bc
Calculation:
According to the question,
Let the time taken by B to complete the work = x days
The time taken by A to complete the work = x + 10 days
The amount of work done = (x)(x + 10)
Efficiency of A = x+10(x)(x+10) = x units a day
Efficiency of B = x(x)(x+10) = (x + 10) units a day
Now,
The amount of work done by A in 5 days = 5x
The amount of work done by B in 5 days = 5(x + 10) = 5x + 50
The total amount of work done in 5 days = 5x + 5x + 50 = 10x + 50
Again according to the question,
⇒ 10x + 50 = 158 of (x)(x + 10)
Now by using the value of option.
Option A: x = 15
⇒ 10(15) + 50 = 158 of (15)(15 + 10)
⇒ 150 + 50 = 8 × 25
⇒ 200 = 200
Therefore, the time is taken by B to complete the work = 15 days
Therefore, '15 days' is the required answer.
<br>
Shortcut Trick
A takes 10 days more than B to finish a task.
They both do the work together for 5 days and finish 158 part of the work.
<br>
⇒ 158(Total work) = 5 Days
<br>
⇒ Total work = 815×5 Days
⇒ Total work = 75/8 Days ..... (1)
<br>
Now we will help from the option,
<br>
Option (1) - B = 15 Days
⇒ A = 15 + 10 = 25 Days
| Time | Efficiency | Total work |
|---|
| A | 25 | 3 | 75 |
| B | 15 | 5 | |
<br>
⇒ They both do the work together,
⇒ EfficiencyTotalwork=875 Days, which is equal to the value given in eq (1)
<br>
Hence, the correct answer is 15 days.