What value should come in place of the question mark (?) in the following question ? 3 / 8 of 5 / 7 of 2 / 5 of 1680 = ?

(a) ? = 443 × 163 – 186782  = 348913664 – 348867684  = 45980

(b) ?=20/3 ÷ 24/5 =20/6 x 5/24 =25/18 = 1 7/18

The series is as follows starting from the second number denote the previous number in the series by x. x × 1 + 1 × 7, x × 2 + 2...

The series is as follows starting from second number x × 1 + 12 , x × 2 + 22, x ×3 + 32, x × 4 + 42, x ×5...

(c) The given number series is based on the following pattern: 18 × 2 + 2 × 1 = 38 38 × 3 + 3 × 2 = 120 120 × 4 +...

(c) The series is as follows × 1 + 2, × 2 + 3, × 3 + 4, ...

(b) The series is as follows  × 0.5 + 0.5, × 1 + 1, + 1.5 + 1.5, ....

(a) The series is as follows x2x1/3,x4x1/5,.......

(b) The pattern of the series is as follows × 12, × 22, × 32, × 42, × 52 Hence, required number = 1728.

(d) The pattern of the series is as follows : 8 × 2.5 = 20 20 × 2.5 = 50 50 × 2.5 = 125  ? = 125 × 2.5 = 312.5