The task is to generate the correct answer for a given math problem.

Problem: at what rate percent on simple interest will rs . 750 amount to rs . 900 in 8 years ?
2.5 %

Problem: a sum of money at simple interest amounts to rs . 815 in 3 years and to rs . 878 in 4 years . the sum is :
626

Problem: calculate how many seconds it will take for 4 bells to toll together again , given that they begin to toll together respectively at the intervals of 9 , 12 , 15 and 18 seconds ?
180