The sum of the first 5 terms of an arithmetic series is 70. The sum of the first 10 terms of this arithmetic series is 210. What is the first term of the series?

Answer 1

1st 5 terms sum ... 5 a + 10 d = 70

1st 10 terms sum ... 10 a + 45 d = 210

solve the system for a

Answer 2

The answer is 42/5

Answer 3

R_scott - your answer was correctish, but not completed.
the answer is 42/5 because 210 was not the solution to the asked question. See if you can use what you found to create 2 equations to get the answer :D