Explanation:

The numbers are squared in ascending order

In first circle,

(3)2 = 9

(4)2 = 16

(5)2 = 25

(6)2 = 36.

In second circle,

(4)2 = 16

(5)2 = 25

(6)2 = 36

(7)2 = 49.

In third circle,

(6)2 = 36

(7)2 = 49

(8)2 = 64

(9)2 = 81.

Explanation:

Solution:

5 × 4 × 8 = 160

7 × 8 × 6 = 336

So, missing number = 9 × 2 × x = 108 ⇒ x = 108 ÷ 18 = 6

Solution:

Number at the centre is the sum of the numbers in the row and column.

83 – (25 + 41) = 83 – 66 = 17

83 – (25 + 26) = 83 – 51 = 32

83 – (41 + 31) = 83 – 72 = 11

So, missing number = 83 – (26 + 31) = 83 – 57 = 26

Age of Shan = 55 years
Age of Sathian = 55-5 = 50 years
Age of Balan = 50-6 = 44 years
Age of Deven = 44-7 = 37 years
Thus, difference between Devan and Shan,
= 55 -37
= 18.