Question

5, 3.5, 5, ?, 21.5, 56.75
​

Answer 1

The missing number (?) is "9.5".

Step-by-step explanation:

The given series are:

5, 3.5, 5, ?, 21.5, 56.75

To find, missing number(?) = ?

​The pattern follow,

$\times \frac{1}{2} + 1, \times \frac{2}{2} + 1.5,$, $\times \frac{3}{2} + 2, \times \frac{4}{2} + 2.5,$, ......

$3.5 = 5\times \frac{1}{2} + 1 =2.5 + 1 = 3.5$

$5 = 3.5\times \frac{2}{2} + 1.5 =3.5 + 1.5 = 5$

? = $= 5\times \frac{3}{2} + 2 =7.5 + 2 = 9.5$

$21 = 9.5\times \frac{4}{2} + 2.5 =19 + 2.5 = 21.5$

$56.75 = 21.5\times \frac{5}{2} + 3 = 53.75 + 3 = 56.75$

Hence, the missing number (?) is "9.5".