Question

A box contains 20 tickets, some are black and others are red. If a ticket is drawn at random from the box, the probability of getting a red ticket is $\frac{1}{4}$. Find the number of black tickets in the box.

• A. 5
• B. 15
• C. 10
• D. 12

Answer 1

The correct option is B 15

Given, probability of getting a red ticket = $\frac{1}{4}$
Total no. of red ticket in the box = 20
$\text{P (drawing a red ticket )}=\frac{\text{no. of red tickets in the box}}{\text{total no. of tickets in the box}}$

As probability of getting red ticket is given, Assume there are '$x$' no. of red tickets.
Favorable no. of outcomes = $x$
$\therefore$ $\frac{1}{4}$= $\frac{x}{20}$
$\Rightarrow x=5$
Number of black tickets in the box $=20-5=15$