Question: The first term in an arihmetic series is 25 and the 3rd term is 19. Find the number of terms in the series if its is 82.

Here's what I did to find d
a+2d=19; 25+2d= 19 ;19-25=2d d=-6/2=-3

This is where I'm stuck. Can you please provide me with some guidance.

Thanks

Aana

Hi Aana,

I think your second sentence should read

Find the number of terms in the series if its sum is 82.

You have the three terms 25, 22, 19. What is their sum? What is the next term? What is the sum of the 4 terms? What about 5 terms?

Penny