instruction:
The task is to generate the correct answer for a given math problem.
question:
Problem: find the area of trapezium whose parallel sides are 20 cm and 18 cm long , and the distance between them is 20 cm ?
answer:
380 cm 2

question:
Problem: mary can do a piece of work in 26 days . rosy is 30 % more efficient than mary . the number of days taken by rosy to do the same piece of work is ?
answer:
20

question:
Problem: the population of a town is 8000 . it decreases annually at the rate of 10 % p . a . what was its population 2 years ago ?
answer:
9876