Question

If the speed ($y$) and the time ($x$) are inversely related, what is the speed of the car at $t=20$?

• A. $y=4$km/h
• B. $y=8$km/h
• C. $y=12$km/h
• D. $y=16$km/h

Answer 1

The correct option is C $y=12$km/h


If the speed ($y$) and the time ($x$) are inversely related, then their product is constant in other words $xy=K$ where, $K$ is the constant of proportionality.

$K=240\times 1=120\times 2=240$

Hence, at $t=20$,

$240=20y$

$y=12$km/h