Question

2. Find the next three terms in the sequence.

2.5, 5, 10, 20, ...
A 40, 80, 160
B 25, 30, 35
C 50, 100, 200
D 30, 40, 50

Answer 1

A 40, 80, 160

Explanation:

Given:

2.5, 5, 10, 20, ...

geometric sequence has a constant ratio r and is given by

an=a1r(r)^(n-1)

where

an=nth term

r=common ratio

n=number of term

a1=first term

In given series:

a1=2.5

r= a(n+1)/an

r=5/2.5

r=2

Now computing next term a5

a5=a1(r)^(n-1)

= 2.5(2)^(4)

= 40

a6=a1(r)^(n-1)

= 2.5(2)^(5)

=80

a7=a1(r)^(n-1)

= 2.5(2)^(6)

=160

So the sequence now is 2.5, 5, 10, 20,40, 80, 160!