Question

A11 if a3=5/16 and r=2

Answer 1

80

Explanation:

The n th term of a geometric sequence is

`a_(n)` = a₁
`(r)^(n-1)`

where a₁ is the first term and r the common ratio

We require to find a₁

Given

a₃ =
`(5)/(16)`, then

a₁r² =
`(5)/(16)`, that is

a₁ ×2² =
`(5)/(16)` ( divide both sides by 4 )

a₁ =
`(5)/(64)`, thus

`a_(11)` =
`(5)/(64)` ×
`2^(10)` =
`(5)/(64)` × 1024 = 5 × 16 = 80