UPSC NDA Math Model Paper 10

Here, P(L) = 0.03, P(M) = 0.04, P(N) = 0.02
Probability that toy stops working
P(L ∪ M ∪ N) = 0.03 + 0.04 + 0.02 - (0.03 × 0.04) - (0.04 × 0.02) - (0.03 × 0.02) + 0.03 × 0.04 × 0.02
= 0.09 - 0.0012 - 0.0008 - 0.0006 + 0.000024
= 0.087
Probability that the toy will not stop working
1 - P(L ∪ M ∪ N) = 1 - 0.087
= 0.9
Hence , option (3) is correct.