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ITT: Why the GRE is harder than the LSAT
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Date: May 1st, 2012 3:35 PM
Which quantity is greater?
A: The units digit of 13 × 13^13 B: The units digit of 19 × 19^19 |
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Date: May 1st, 2012 4:11 PM
you should memorize your squares up to around 15, so you have the first one covered. honestly you should be able to figure out the units digit of for 19 in your head, but even if not you take 20 seconds to do 19^2 by hand and you have your answer. (A, ftr)
(not necessarily saying the LSAT is harder than the GRE, also ftr) |
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Date: May 1st, 2012 4:14 PM |
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Date: May 1st, 2012 4:16 PM |
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Date: May 1st, 2012 4:18 PM |
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Date: May 1st, 2012 4:18 PM |
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Date: May 1st, 2012 4:20 PM |
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Date: May 1st, 2012 4:21 PM |
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Date: May 1st, 2012 4:36 PM |
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Date: May 1st, 2012 5:25 PM
13*13^13=13^14. and since only units digit matters, 3^14 units digits:3^0=1 3^1=3, 3^2=9, 3^3=7, 3^4=1, at that point the pattern repeats, so 14/4=3 remainder 2. so raise by the remainder to get the units digit= 9.
19*19^19=19^20 ==> 9^20. units digits: 9^0=1, 9^1=9, 9^2=1 at that point the pattern repeats, so 20/2=10 remainder 0. so raise by the remainder to get the units digit = 1.
therefore A is correct, and should've been answered by a person of reasonable problem-solving ability in less than 30 seconds. |
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Date: May 1st, 2012 4:14 PM |
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Date: May 1st, 2012 4:16 PM |
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Date: May 1st, 2012 4:26 PM
edit: and i think 7 for A (off the top of my head) |
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Date: May 1st, 2012 4:28 PM |
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Date: May 1st, 2012 4:30 PM
edit: i fucked this up more than i though. lol, *leaves in shame* |
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Date: May 1st, 2012 4:31 PM |
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Date: May 1st, 2012 4:28 PM |
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Date: May 1st, 2012 4:32 PM |
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Date: May 1st, 2012 5:30 PM |
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Date: May 1st, 2012 5:32 PM |
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Date: May 1st, 2012 7:46 PM |
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Date: May 1st, 2012 7:47 PM |
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Date: May 1st, 2012 8:47 PM |