Question

A box contains 20 tickets, some are black while the others are red. If a ticket is drawn at random from the box, the probability of getting a red ticket is 0.25. Find the number of black tickets in the box.

• A. 15

Answer 1

The correct option is A 15
$\text{Given, probability of getting a red}\text{ticket}=0.25=\frac{25}{100}=\frac{1}{4}$

$\text{Total no. of red ticket in the box}=20$

$\text{P (drawing a red ticket )}=\frac{\text{Number of red tickets in the box}}{\text{Total number of tickets in the box}}$

Let the number of red tickets be $x.$

$\text{So, the number of favourable outcomes =}x\therefore \frac{1}{4}=\frac{x}{20}\Rightarrow 4x=20\Rightarrow x=5$

$\text{So, the number of black tickets}=20-5=15$