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July 31, 2015

Posted by **sarah** on Sunday, June 5, 2011 at 5:17pm.

7, 11, 15, 19, 23

- maths -
**MathMate**, Sunday, June 5, 2011 at 5:22pmIs this an arithmetic progression (AP) or geometric progression (GP)?

AP's have constant differences, while GP's have constant ratios.

Given series:

7, 11, 15, 19, 23

differences:

11-7=4, 15-11=4, 19-15=4, 23-19=4

(constant difference d=4, therefore AP)

ratios:

11/7, 15/11, 19/15, 23/19 (different, so NOT GP).

The nth term of an AP is:

A(n)=A(1)+(n-1)d

d=4

A(n)=A(1)+(n-1)d

=7+(n-1)4

=7+4n-4

=3+4n

- maths -
**katie**, Sunday, June 5, 2011 at 5:23pmit just says work out the nth term for the those numbers

- maths -
**MathMate**, Sunday, June 5, 2011 at 5:37pmI hope you did not just read the first line of my response.

I was asking myself that question (hope you do the same). The rest of the response followed.