Problem:
Assume 0<r<3. Below are five equations for x. Which equation has the largest solution x ?
Answer Choices:
A. 3(1+r)x=7
B. 3(1+r/10)x=7
C. 3(1+2r)x=7
D. 3(1+r)x=7
E. 3(1+1/r)x=7 Solution:
Rearrange the equations to the form
x=log(1+f(r))log(37)
Because f(r) is positive, for each answer choice, x will be largest when f(r) is the smallest. Because r>0, we have 10r<r<2r. Because r2<9<10 we have 10r<r1. Finally, r<10, so 10r<r.