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2006 Cyprus MO/Lyceum/Problem 10

Revision as of 20:17, 17 October 2007 by Azjps (talk | contribs) (sol)

Problem

If $2^x=15$ and $15^y=256$, then the product $xy$ equals

A. $7$

B. $3$

C. $1$

D. $8$

E. $6$

Solution

$(2^x)^y = 2^{xy} = 256$, so $xy = 8\ \mathrm{(D)}$.

See also

2006 Cyprus MO, Lyceum (Problems)
Preceded by
Problem 9 		Followed by
Problem 11
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 • 26 • 27 • 28 • 29 • 30
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