GATE 2026 MT – Question 33
A box contains 20 thermometers, 3 of which are defective. One person randomly draws 2 thermometers from the box, one-by-one, without replacement. The probability in percent (rounded-off to two decimal places) that none of these TWO thermometers is defective, is ________________ %.
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Correct answer: 71.00 to 72.00
Explanation
There are $20-3=17$ good thermometers. The probability that the first is good is $17/20$. Without replacement, the conditional probability that the second is good is $16/19$.
Thus $P=(17/20)(16/19)=0.715789\ldots$. As a percentage, this is **71.58%**.