J's answer to mint's Junior College 1 H2 Maths Singapore question.
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Since we need to use both 'A's, we are left with DVNCE to choose the 2 remaining letters from.
Number of ways to choose 2 letters from 5 unique letters = 5C2 = 5! / (2!(5-2)!) = 5! / (2×3!) = (5 x 4) / 2 = 20 /2 = 10
For each way chosen, number of ways to permuate two 'A's and two other unique letters = 4! / 2! = 24 / 2 = 12
Total number of ways = 10 x 12 = 120
Since we need to use both 'A's, we are left with DVNCE to choose the 2 remaining letters from.
Number of ways to choose 2 letters from 5 unique letters = 5C2 = 5! / (2!(5-2)!) = 5! / (2×3!) = (5 x 4) / 2 = 20 /2 = 10
For each way chosen, number of ways to permuate two 'A's and two other unique letters = 4! / 2! = 24 / 2 = 12
Total number of ways = 10 x 12 = 120
Date Posted:
4 years ago
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