GWD18-6

[EmmaCYC]

Q6:
The function f is defined for each positive three-digit integer n by f(n) = 2x 3y 5z, 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

答案D

題目根本看不懂...

[scujean]

cd's ans

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