Given: Time taken by Ramesh and Rajesh to do the work together = 12 days Calculation: Let the time taken by Ramesh and Rajesh to do the work alone be x and y respectively. Then, Ramesh’s and Rajesh’s 1 day work is equal to x1​ and y1​ respectively ⇒ (x1​)+(y1​)=121​ ...(i) Ramesh reduced his efficiency by half then time taken to complete the work by both of them is increased by 50%. ⇒ Ramesh’s 1 day work =2x1​ ⇒ Time taken by them to finish the work =12×(100150​)=18 days ⇒ 2x1​+y1​=181​ ...(ii) Solving (i) and (ii) x = 18 and y = 36 ∴ Time taken by Rajesh to finish the work alone is 36 days