Answer: 140
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Step-by-step explanation:
The unique digits are: 9, 6, 1
- 9 shows up once
- 6 shows up three times
- 1 shoes up three times
There are 1+3+3 = 7 digits with the repeats mentioned. If we could somehow tell the 6's apart and the 1's apart, then we'd have 7! = 7*6*5*4*3*2*1 = 5040 different permutations.
But because we can't tell the 6's apart, nor the 1's apart, this means we have to divide by (3!*3!). Each 3! represents the number of times the 6's show up and same goes for the 1's.
So (5040)/(3!*3!) = 5040/(6*6) = 5040/36 = 140 is the number of ways to rearrange the digits