PATTERNS, FUR1 2011 VCAA 1 MC

Stefan swam laps of his pool each day last week.

The number of laps he swam each day followed a geometric sequence.

He swam 1 lap on Monday, 2 laps on Tuesday and 4 laps on Wednesday.

The number of laps that he swam on Thursday was

A. `5`

B. `6`

C. `8`

D. `12`

E. `16`

Show Answers Only

`C`

Show Worked Solution

`text(Sequence is 1, 2, 4, …`

`text(GP where)\ \ \ a`	`= 1, and`
`r`	`= t_2 / t_1 = 2`

`T_n = ar^(n-1)`

`:. T_4\ text{(Thurs)}`	` = 1 xx 2^3`
	` = 8`

`=> C`