The first four terms of a geometric progression are 84, 42, 21, 10.5 a) write down the common ratio of the progression b) write down the fifth term of the progression

r = 0.5 and 5.25

Step-by-step explanation:

The common ratio r of a geometric progression is the ratio of a term to the one before it, that is

(a)

r = 42 : 84 = 0.5

(b)

To obtain a term in the sequence multiply the previous term by r, thus

a₅ = 10.5 * 0.5 = 5.25