PATTERNS, FUR1 2015 VCAA 1 MC

The first four terms in a geometric sequence are: `5, 10, 20, 40, …`

The fifth term in this sequence is

A. `45`

B. `50`

C. `60`

D. `80`

E. `100`

Show Answers Only

`D`

Show Worked Solution

`text(GP where)\ \ \ a`	`=5, and`
`r`	`=t_2/t_1=10/5=2`

`t_n`	`=ar^(n-1)`
`t_5`	`= 5 xx 2^4`
	`= 80`

`=> D`