Find the missing number in the series given below. 5, 20, 80, ?, 1280

The correct answer is Option (4) → 320

Each term is four times the term before:

• \(5\times4=20\)

• \(20\times4=80\)

• \(80\times4=320\)

• Check: \(320\times4=1280\), the last term

So the missing number is 320.