If the average of 10% of a number, 25% of that number, 50 % of that number and 75% of that number is 24, then the number will be

The correct answer is (b) 60.

Let $x$ be the number. Then,

$$\frac{10}{100}x + \frac{25}{100}x + \frac{50}{100}x + \frac{75}{100}x = 24$$

$$\frac{150}{100}x = 24$$

$$x = \boxed{60}$$

Each option can be verified by substituting it into the equation.