# CBSE Class 10 Math Question Paper 2016 | Q20

###### CBSE Maths Board Paper Solution | 3 Mark | Probability of Tossing Coins

The given question is a medium difficulty 3-mark question from the chapter Probability. The question has 3 parts one each to compute probability for a specific outcome when three different coins are tossed together. This probability question and appeared in Section C of the 2016 CBSE class 10 board paper.

Question 20: Three different coins are tossed together. Find the probability of getting
(iii) at least two tails

## NCERT Solution to Class 10 Maths

### Explanatory Answer | CBSE 2016 Maths Paper Q20

3 different coins are tossed.
Total number of possibilities = 2 × 2 × 2 = 8
The 8 outcomes are HHH, HHT, HTH, THH, TTH, THT, HTT and TTT

##### (i) Probability of getting exactly 2 heads

Possible outcomes HHT, HTH, THH = 3 outcomes
∴ Probability = $$frac{\text{Number of outcomes of getting exactly 2 heads}}{\text{Total number of outcomes}}$ = $\frac{3}{8}$ #####$ii) Probability of getting at least 2 heads

What does "at least 2 heads" mean?
Outcomes with 2 heads or 3 heads: HHT, HTH, THH, HHH = 4 outcomes
∴ Probability = $$frac{\text{Number of outcomes of getting at least 2 heads}}{\text{Total number of outcomes}}$ = $\frac{4}{8}$ = $\frac{1}{2}$ #####$iii) Probability of getting at least 2 tails

What does "at least 2 tails" mean?
Minimum of 2 tails. i.e., 2 tails or 3 tails
Outcomes with 2 tails or 3 tails: TTH, THT, HTT, TTT = 4 outcomes
∴ Probability = $\frac{\text{Number of outcomes of getting at least 2 tails}}{\text{Total number of outcomes}}$
= $\frac{4}{8}$ = $\frac{1}{2}$

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