Correct Answer - Option 1 :
\(8\frac{3}{4}\)
Given: work together how many days will it take them to complete the work?
R can do work = 15 days
K can do work = 21 days
Concept used:
Total work = LCM
Formula used:
Efficiency = Work/Time
Calculations:
Total work = LCM of 15 and 21 = 105
Person
|
Time
|
Total work
|
Efficiency
|
R
|
15 days
|
105
|
105/15 = 7
|
K
|
21 days
|
105
|
105/21 = 5
|
R + K
|
= 105/12
= 8(3/4) days
|
105
|
12
|
Then efficiency of R+K = 7 + 5 = 12
The efficiency of R ∶ K = 7 ∶ 5
∴ Working together they completed the work in 8(3/4) days.