If the formula R = -0.037t + 50.1 can be used to predict the world record in the 400 meter dash t years after 1925, for what years will the world records be 48.1 seconds or less?

Answer 1

R = -0.037t + 50.1 <= 48.1
-0.037t <= -2
t >= 54.05

So, we need to be at least 55 years after 1925, or 1980.

In fact, according to the livestrong web site:

The International Association of Athletics Federation first recognized the 400-meter dash record in 1900, when it was set by the United States' Maxey Long in 47.8 seconds.