Question

In three of the following four number pairs, the numbers are related in the same way and thus form a group. Which number pair DOES NOT belong to that group? (NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into their constituent digits. E.g. 13 – Operations on 13 such as adding / subtracting /multiplying to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)

• A. 5 : 30
• B. 10 : 110
• C. 8 : 70
• D. 3 : 12

Answer 1

Answer:

C. 8 : 70

The number pair that DOES NOT belong to that group is 8 : 70.

The relationship between the first number ($x$) and the second number in each pair follows the pattern:
$x \rightarrow (x^2 + x) \quad \text{or} \quad x \times (x + 1)$

Let's test this logic against each option:

• 3 : 12 $\rightarrow 3^2 + 3 = 9 + 3 = \mathbf{12}$ (Follows pattern)

• 10 : 110 $\rightarrow 10^2 + 10 = 100 + 10 = \mathbf{110}$ (Follows pattern)

• 8 : 70 $\rightarrow 8^2 + 8 = 64 + 8 = \mathbf{72}$ (Does NOT follow pattern)

Since 8 : 70 results in 70 instead of 72, it is the odd one out.