Question

The tempature is -3 degress.The temperature is expected to decrease 2.5 degress each hour until the temperature reaches -18 degress. How many hours will it take to reach -18? A 6hours
B 7 hours
C 7.2 hours
D 8.4 hours

Answer 1

We can set this problem up as an algebraic equation, which we can then solve to find our answer.

We start at -3. So we can start our equation with that:

$-3$

However, this doesn't represent any change in temperature, just that we start at -3. To show change, we will use the variable $x$, where $x$ stands for the number of hours. Each hour accounts for a change of -2.5 in degrees, meaning that we must multiply our $x$ by -2.5. We can now add this term into our equation:

$-3 - 2.5x$

We are trying to find when we will reach -18 degrees, so we will set our entire equation equal to -18 and solve:

$-3 - 2.5x = -18$

$-2.5x = -15$

$x = 6$

It will take us 6 hours, or choice A.