Mathematics - Permutation & Combination Question with Solution | TestHub

MathematicsPermutation & CombinationnPr & nCrMedium2 minPYQ_2022

MathematicsMediumsingle choice

The number of different seven-digit numbers that can be written using only the three digit 1 , 2 and 3 with the condition that the digit 2 occurs twice in each number is

Options:

Answer:

Solution:

Other than 2, remaining five places can be filled by 1 and 3 for each place. The number of ways for five places is $2 \times 2 \times 2 \times 2 \times 2 = 2^{5}$ . For 2 , selecting 2 places out of 7 is $^{7} C_{2}$ . Hence, the required number of ways is $^{7} C_{2} \times 2^{5}$ .

Stream:BITSATSubject:MathematicsTopic:Permutation & CombinationSubtopic:nPr & nCr

⏱ 2mℹ️ Source: PYQ_2022

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