Arithmetic progression

[anakbulan]

An AP has 11 terms. The sum of the first 8 terms is 108 and the sum of all the even terms is 45.
Find
(a) the 9th term (b) the sum of the first 5 terms

 

[Dr.Peterson]

Please show what you've done so far, so we can know what help you need.

Presumably you know some formulas; at the least, show us what they are.

 

[Steven G]

A1 = a
A2 = a + d
A3 = a + 2d
A4 = a + 3d
A5 = a + 4d
A6 = a + 5d
A7 = a + 6d
A8 = a + 7d
Sum of above is 108

A2 = a + d
A4 = a + 3d
A6 = a + 5d
A8 = a + 7d
A10=a + 9d
sum of the above is 45

Did you get that far?

There are two unknowns d and a. Now armed with the two above equations you can solve for a and d.