A bag contains 6 white and 4 black ball. Two balls are drawn at random. Then the probability of getting balls of the same colour is ____.

$\frac{7}{15}$

We are given 6 white and 4 black balls and we have been asked to find the probability of drawing 2 balls of the same colour.

Number of ways of drawing 2 balls out of 10.
2 balls can be drawn out of 10 balls in the following number of ways –

¹⁰C₂ = 45

Total outcomes are 45.

Favourable items = n(2 white balls appear) + n(2 black balls appear)
Favourable items = ⁶C₂+⁴C₂ = 15 + 6 = 21

Required Probability = 21/45 = 7/15

The correct answer is Option (4) → $\frac{7}{15}$

10C2=4510C2=45