Natasha earned the following test grades: 76, 84, and 77. What grade would she need to earn on then fourth test to have an average of at least an 80?

Question

I can't colve this, please help!

Answer 1

t represents the fourth test score

(76 + 84 + 77 + t) / 4 = 80

Can you solve for t and answer?

Answer 2

76 is 4 under 80

84 is 4 over 80

77 is 3 under 80

83 is 3 over 80

83 is what you need, 76 and 84 average to 80

77 and 83 average to 80

You need at least an 83 to get an 80 average

Answer 3

How do you solve for the average for a set of test grades?

average test grade = (test grade 1 + test grade 2 + test grade 3 + test grade 4) /n, where n is the number of test grades

What does test grade 4 need to be to get an average grade of 80?

Now define the variables

average test grade = 80

test grade 1= 76

test grade 2 = 84

test grade 3 = 77

test grade 4 = x

n = 4

Plug the variables into the formula above

80 = (76 + 84 + 77 + x) /4

Now simplify the equation

80 = (237 +x) /4

Now solve for x

80 * 4 = (237 +x) /4 *4

320 = 237 + x

320 - 237 = 237 - 237 + x

x = 83

Now plug x back into the equation to check your answer

80 = (76 + 84 + 77 + 83) /4

80 = 80