Question

To get a b in​ math, alexandria pappas must average 80 on five tests. scores on the first four tests were 8383​, 7373​, 8383​, and 7777. what is the lowest score that she can get on the last test and still get a​ b?

Answer 1

The average of a set of numbers is the sum of those numbers, divided by how many they are.

So, if we call the fifth score $x$, our dataset is

$83,\ 73,\ 83\, 77,\ x$

And their average is

$\dfrac{83 + 73 + 83 + 77 + x}{5} = \dfrac{316+x}{5}$

We want this quantity to be at least 80, so we ask

$\dfrac{316+x}{5} \geq 80 \iff 316+x \geq 400 \iff x \geq 400-316 = 84$

So, pappas must score at least 80.