Question

Marks)

9 (b). The first two terms of an arithmetic progression are shown.
р
5p
The sum of the first three terms is 90
Work out the value of p.

Answer 1

9514 1404 393

Answer:

p = 6

Explanation:

The difference between the first two terms is ...

5p -p = 4p

Since this is an arithmetic sequence, the next term will be 4p more than the last term:

5p +4p = 9p

Then the sum of the first three terms is ...

p + 5p + 9p = 90

15p = 90 . . . . . . . . . . collect terms

p = 6 . . . . . . . . . . . . divide by 15

_____

The first three terms are 6, 30, 54.