CBSE · Class 6-12

Class 9 · Ganita Manjari

Unit 8 · Class 9Ganita Manjari

Predicting What Comes Next: Sequences and Progressions

Arithmetic and geometric progressions, general terms, sums.

Lessons

4 concepts

1
Arithmetic Progression
Fixed jump between consecutive terms. $2, 5, 8, 11, \ldots$ has $a=2, d=3$ . Nth term: $a + (n-1)d$ .
2
Sum of AP
$S_n = \tfrac n2(a + l)$ where $l$ is last term. Or $S_n = \tfrac n2 [2a + (n-1)d]$ .
3
Geometric Progression
Fixed ratio between consecutive terms. $3, 6, 12, 24, \ldots$ has $a=3, r=2$ . Nth term: $ar^{n-1}$ .
4
Real-Life
AP: salary increments, seat rows. GP: compound interest, bacterial growth.

Skills to practise

Skill · medium

Predicting What Comes Next: Sequences and Progressions — Practice