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Source: — Data Sufficiency |
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by cans » Thu Sep 15, 2011 8:57 pm
(243)^x* (463)^y = n
x+y=7 sufficient. unit digit is 7.
x=4 insufficient. y not known.
IMO A
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by jogi1984 » Thu Sep 15, 2011 9:19 pm
Hi Cans,
Thanks a lot...
but how to go for it ..Does 463 have sm factors of 3 ???
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by 1947 » Sat Sep 17, 2011 1:36 am
(243)^x* (463)^y = n
x+y=7 sufficient. unit digit is 7.

3^x repeats like 3,9,27,81,243 i.e. after every 4 powers unit digit is 3.
243 = 3^5
since 243 also ends with 3 so if 243 has any factor of 3 becomes meaningless...
what question is asking is what is the unit digit of 3^(x+y)
since x+y = 7 we can find the unit digit.
let me know if it explains
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