Question

A box contains 10 black and 10 white balls. The probability of drawing two balls of the same colour, is ?

• A. $\frac{9}{19}$
• B. $\frac{9}{38}$
• C. $\frac{10}{19}$
• D. $\frac{5}{19}$

Answer 1

The correct option is C $\frac{10}{19}$

Number of black balls$=10$

Number of white balls$=10$

Total number of balls$=10+10=20$

probability of drawing two balls of the same colour$=\frac{{{10}_C}_1\times {{10}_C}_1}{{{20}_C}_2}=\frac{10\times 10}{\frac{20!}{18!2!}}=\frac{100}{\frac{20\times 19}{2}}=\frac{10}{19}$