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GRE 3-Four persons enter the lift of a seven storey building at the ground floor...

By spartan
Four persons enter the lift of a seven story building at the ground floor. In how many ways can they get out of lift on any floor other than ground floor

A. 720
B. 1296
C. 1540
D. 1478
E. 360
Each person out of 4 has 6 floors (options) to get out of (since no one gets out on the ground floor), hence total ways is 6*6*6*6=6^4. Now, there is no need to actually calculate this value: 6^4 will have 6 as the units digit and there is only one option (B) which offers such a number.

Answer: B.
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