Question

Find the missing number (X and Y) in the series and find the value of Y - X: 

10, 30, 20, X, 50, 150, Y

1. 10
2. 80
3. 90
4. 100

Answer 1

Correct Answer - Option 1 : 10

Given:

10, 30, 20, X, 50, 150, Y

Calculation:

The given series consists of two series,

The 1^st series is

⇒ 10, 20, 50, Y

The pattern followed by the 1^st series is, difference between the terms is increased by 20

⇒ 20 – 10 = 10

⇒ 50 – 20 = (10 + 20)

⇒ Y – 50 = (10 + 20 + 20)

Solving for Y

⇒ Y – 50 = 50

⇒ Y = 100

The 2^nd series is

⇒ 30, X, 150

If we observe the 2^nd series, we can see difference between 30 and 150 is 120, so dividing the difference by 2 we get 60. So, 2^nd series follows the increment of 60

⇒ X – 30 = 60

⇒ X = 90

⇒ The value of Y – X = 100 – 90 = 10

∴ The value of Y – X is 10