Question

Lisa’s test grades are 79, 89, and 90. There will be one more test this year. If Lisa wants her test average to be at least 88, what is the lowest grade she can get on her last test?

Answer 1

Answer:  The lowest grade that Lisa can get in her last test is 94.

Step-by-step explanation:  Given that Lisa’s test grades are 79, 89, and 90 and there will be one more test this year.

We are to find the lowest grade Lisa can get on her last test if she wants her test average to be at least 88.

Let x represents the grade that Lisa get in her last test.

Then, according to the given information, we have

$\dfrac{79+89+90+x}{4}\geq 88\\\\\\\Rightarrow \dfrac{258+x}{4}\geq 88\\\\\Rightarrow 258+x\geq4\times 88\\\\\Rightarrow 258+x\geq 352\\\\\Rightarrow x\geq 352-258\\\\\Rightarrow x\geq 94.$

Thus, the lowest grade that Lisa can get in her last test is 94.

Answer 2

You would have to at least get a 94 on the next test to keep above an 88.