Carcass wrote:
For any three-digit number, \(abc\), \(*abc*=(3^a)(5^b)(7^c)\). What is the value of \((g-f)\) if \(f\) and \(g\) are three-digit numbers for which \(*f*=(3^r)(5^s)(7^t)\) and \(*g*=(25)(*f*)\)?
A. 250
B. 220
C. 200
D. 20
E. 2
In \(*f*=(3^r)(5^s)(7^t)\), Let \(r = 1\), \(s = 1\), \(t = 1\)
\(a = 1\), \(b = 1\), \(c = 1\)
i.e. \(f = 111\)
Now, \(*g*=(25)(*f*) = 5^2(3^r)(5^s)(7^t) = (3^r)(5^{s+2})(7^t)\)
Plug \(r = 1\), \(s = 1\), \(t = 1\)
\(a = 1\), \(b = 1 + 2 = 3\), \(c = 1\)
Therefore, \(g = 131\)
\(g - f = 131 - 111 = 20\)
Hence, option D