A box contains nine bulbs out of which 4 are defective. If four bulbs are chosen at random, find the probability that all the four bulbs are defective.
Correct answer: D. 1/126
- A. 62/63
- B. 125/126
- C. 1/63
- D. 1/126
Explanation
To select all four defective bulbs, there is C(4,4) = 1 favorable selection. The total ways to select four bulbs from nine are C(9,4) = 126, so the probability is 1/126. Students may choose 125/126 by calculating the complementary event, at least one good bulb.
Last updated
About Ratio and Proportion
Ratios compare quantities in the same units, while proportions state that two ratios are equal. Problems cover simplification, division in a given ratio, direct and inverse variation, scale, and missing terms, with attention to the difference between a ratio and a fraction representing part of a whole.
Practise Arithmetic
1,060 free Arithmetic MCQs from Mathematics, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Exams that ask Mathematics questions like this
Mathematics is on 67 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.