gwd 18--6

wanze

Q6:

The function f is defined for each positive three-digit integer n by f(n) = 2^x 3^y 5^z, where x, y and z are the hundreds, tens, and units digits of n, respectively.  If m and v are three-digit positive integers such that f(m) = 9 f(v), then m - v =

A.       8

B.       9

C.     18

D.     20

E.      80  

为啥选20, 没思路

不知不觉

f(m)=9f(v)=3^2*2^x*3^y*5^z=2^x*3^(y+2)*5^z

m-v= (100x+10(y+2)+z)-(100x+10y+z)=20

wanze

非常感谢

zt123

Thanks for my devoted companion~