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Mathematics · 2024 · 3 marks
CBSE 2024 · Region 4 · Set 1 · Q27
(a) Three coins are tossed simultaneously. What is the probability of getting (i) at least one head? (ii) exactly two tails? (iii) at most one tail?
(a)
Three coins are tossed simultaneously. What is the probability of getting
(i)
at least one head ?
(ii)
exactly two tails ?
(iii)
at most one tail ?
OR
(b)
A box contains $\displaystyle 90$ discs which are numbered $\displaystyle 1$ to $\displaystyle 90$ . If one disc is drawn at random from the box, find the probability that it bears a :
(i)
$\displaystyle 2$-digit number less than 40.
(ii)
number divisible by $\displaystyle 5$ and greater than 50.
(iii)
a perfect square number.
Marking-scheme solution
Total number of outcomes \(\displaystyle =8\)
(i) P (at least one head) \(\displaystyle =\frac{7}{8}\)
(ii) P (exactly $\displaystyle 2$ tails) \(\displaystyle =\frac{3}{8}\)
(iii) P (at most one tail) \(\displaystyle =\frac{4}{8}\) or \(\displaystyle \frac{1}{2}\)
Total outcomes = $\displaystyle 90$
(i) P ($\displaystyle 2$ digit number less than $\displaystyle 40$\(\displaystyle )=\frac{30}{90}\) or \(\displaystyle \frac{1}{3}\)
(ii) P (a number divisible by $\displaystyle 5$ and greater than $\displaystyle 50$\(\displaystyle )=\frac{8}{90}\) or \(\displaystyle \frac{4}{45}\)
(iii) P (a perfect square number) \(\displaystyle =\frac{9}{90}\) or \(\displaystyle \frac{1}{10}\)
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CBSE Class 10 Mathematics past-paper question from the 2024 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.