Question

Rosa's test scores are 78, 92, 88, and 89. What must she score on her next test to have an average of 90? A) 95 B) 97 C) 99 D) 103

Answer 1

Answer: D

Step-by-step explanation:

Let x represent the score on her next test

$\frac{78 + 92 + 88 + 89 + x}{5} = 90$

$(5)\frac{78 + 92 + 88 + 89 + x}{5} = (5)90$

78 + 92 + 88 + 89 + x = 5(90)

                      347 + x = 450

                    -347         -347

                                x = 103