Question

235:30::578:60::898:75::123:?

Answer 1

Hello friend,

If you observe carefully, you'll notice second number is thrice the sum of all the digits in first number.

For example,
For 235 2+3+5=10
Second number = 10×3=30
For 578 5+7+8=20
Second number = 20×3=60
For 898 8+9+8=25
Second number = 25×3=75

Let's solve this for 123
123 1+2+3=6
Second number = 6×3=18

Hence our answer is 18.

Hope this was useful.

Answer 2

Given:

The series,

235 : 30 :: 578 : 60 :: 898 : 75 :: 123 : ?

Logic:

Thrice the sum of the digits in the left gives the number on the right.

Solution:

Consider 235,

The sum of the digits,

2 + 3 + 5 = 10

10 * 3 = 30

30 is the number to the right of 235.

Similarly for 123,

The sum of the digits,

1 + 2 + 3 = 6

6 * 3 = 18

Hence, 123 : 18

The series is 235 : 30 :: 578 : 60 :: 898 : 75 :: 123 : 18