Which number will replace the question mark?

The correct answer is Option (4) → 4

In each figure, the product of the two numbers at the sides equals the product of the numbers at the top and the bottom. The first two figures show the rule, and it is then applied to the third.

• First figure: \(5\times6=30\) and \(3\times10=30\)

• Second figure: \(6\times6=36\) and \(9\times4=36\)

• Third figure: \(9\times8=72\), so \(18\times?=72\), giving \(?=4\)