From that information and with subtraction, you can say what the sixth term is.

There are two formulas that can be used:

and

So you can make two simultaneous equations in a and d.

Bob

Ani

2013-09-06 16:41:25

Thank you

Fruityloop

2013-09-06 13:50:27

Use the difference between the sums to head towards an answer.

Ani

2013-09-06 12:24:32

I've been sitting for a few hours thinking how to figure out the question below, could you help me solve this in a step-by-step format?

The Question; The sum of the first five terms of an arithmetic series is 85. The sum of the first six terms is 123. What are the first four terms of the series?