Yogananda
What is the sum of all 4 digit numbers that can be formed by rearranging the digits of the number 3345?
A.99990
B.69994
C.79992
D.49995
E.66660
Weird numbers where unique unit digits are in the answer choices indicates that “units digit logic” (for lack of a better term) is the way to go. OP clearly knows how the GMAT works!
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Possible formations of 3345 where 5 is the units digit is determined by the possible formations of 334.
Possible formations of a string of N numbers or letters where repeats exist: N!/x!y!etc!
where x, y, and etc = number of repeats.
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Possible formations of 334: 3!/2! = 3 (three total letters, two repeats).
So possible formations of 3345 where 5 is the units digit = 3
Possible formations of 3345 where 4 is the units digit = 4
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Possible formations of 3345 where 3 is the unit digit is a bit different, because it’s determined by the possible formations of 345 = 3! = 6
So possible formations of 3345 where 3 is the units digit = 6
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The possible formations of 3345 includes three 5s as the units digit, three 4s as the units digit, and six 3s as the units digit.
5 + 5 + 5 + 4 + 4 + 4 + 3 + 3 + 3 + 3 + 3 + 3 = 3(5) + 3(4) + 6(3) = units digit of 5
Only D fits
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