A pair of dice is thrown. Find the probability of getting a sum of 10 or more, if 5 appears on the first dice.

When two dice are thrown simultaneously;

Total number of possible outcomes = 6 × 6 = 36.

For obtaining a sum of 10 or more, if 5 appears on the first dice, the favourable outcomes are :

(5, 5) and (5, 6).

∴ No. of favourable outcomes = 2.

P(getting a sum of 10 or more) = $\dfrac{\text{No. of favourable outcomes}}{\text{No. of possible outcomes}} = \dfrac{2}{36} = \dfrac{1}{18}$.

Hence, the probability of getting a sum of 10 or more, if 5 appears on the first dice = $\dfrac{1}{18}$.