Question 14 - CBSE Class 12 Sample Paper for 2024 Boards - Solutions of Sample Papers and Past Year Papers - for Class 12 Boards
Last updated at August 4, 2026 by Teachoo
A problem in Mathematics is given to three students whose chances of solving it are 1/2, 1/3, 1/4 respectively. If the events of their solving the problem are independent then the probability that the problem will be solved, is
Now,
Probability that the problem is solved
= Probability that A solves the problem or B solves the problem
or C solves the problem
= P(A ∪ B ∪ C)
= P(A) + P(B) + P(C) – P(A ∩ B) – P(B ∩ C) – P(C ∩ A) + P(A ∩ B ∩ C)
Since A ,B & C are independent,
P(A ∩ B) = P(A) . P(B)
= 1/2 × 1/3 = 𝟏/𝟔
P(B ∩ C) = P(B) . P(C)
= 1/3 × 1/4 = 𝟏/𝟏𝟐
P(C ∩ A) = P(C) . P(A)
= 1/4 × 1/2 = 𝟏/𝟖
P(A ∩ B ∩ C) = P(A) . P(B) . P(C)
= 1/2 × 1/3 × 1/4 = 𝟏/𝟐𝟒
Now,
P(Problem is solved) = P(A) + P(B) + P(C) – P(A ∩ B) – P(B ∩ C) – P(C ∩ A) + P(A ∩ B ∩ C)
= 1/2 + 1/3 + 1/4 − 1/6 − 1/12 − 1/8 + 1/24
= 1/2 + 1/3 + 1/4 − (1/6 " " +1/12+1/8) + 1/24 = 12/24 + 8/24 + 6/24 − (4/24 " " +2/24+3/24) + 1/24
= 26/24 − (9/24) + 1/24
= 18/24
= 𝟑/𝟒
So, the correct answer is (d)
Made by
Davneet Singh
Davneet Singh is an IIT Kanpur graduate and has been teaching for 16+ years. At Teachoo, he breaks down Maths, Science and Computer Science into simple steps so students understand concepts deeply and score with confidence.
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