If 20 percent of x equals 80 percent of y, which of the following expresses y in terms of x?
(A) y = 16% of x
(B) y = 25% of x
(C) y = 60% of x
(D) y = 100% of x
(E) y = 400% of x
The Official SAT Study Guide 2006
Today it seems simple and obvious.
This is a classic case of inflexible knowledge. I've practiced solving many, many literal equations over the past few years, a skill I learned and practiced in high school, too. I had no trouble doing it then, and I've had no trouble doing it now.
So, in theory, I 'know' how to do this problem.
And yet when I encountered a literal equation involving percent, I was mystified.
What fresh hell is this?
Funny, I didn't need to set up a formal equation for this. If 20% of x = 80% of y, y must be four times as small as x. Thus, 25% of x.That's the kind of thing years of doing bar models does for you.
Not that cranberry has spent years drawing bar models.