Ella's test grades in her history class are 89, 94, 82, 84, and 98. What score must Ella make on her next test to have a mean test score of 90?

Mean is same as average

to find average

add up terms

divided that sum by the number of terms you have

example

mean of x, y, z

x+y+z

3 terms

(x+y+z) / 3=mean

so

represent next test score as x

89+94+82+84+98+x

count how many terms ther are (6 terms)

mean is 90

(89+94+82+84+98+x) / 6=90

add the like terms

(447+x) / 6=90

multiply both sides by 6 to clear fraction

447+x=540

subtract 447 from both sides

x=93

she needs a score of 93 on next test

She will have to get a 96 on here next test