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

Problem: in an election between two candidates , one got 60 % of the total valid votes , 30 % of the votes were invalid . if the total number of votes was 9000 , the number of valid votes that the other candidate got , was :
2520

Problem: a train 800 m long can cross a pole in 10 sec and then find the speed of the train ?
28

Problem: the s . i . on a certain sum of money for 2 years at 4 % per annum is half the c . i . on rs . 4000 for 2 years at 10 % per annum . the sum placed on s . i . is ?

5250