Question

Sam will take four science tests this quarter. Her scores on three of the tests

are shown below.

Test 1

83%

Test 2

91%

Test 3

88%

Test 4

?

What does Sam need to score on the fourth test to ensure that she will have an

average of 90% for all four tests?

%

Answer 1

98%.

Explanation:

The following data were obtained from the question:

Test 1 (T₁) = 83%

Test 2 (T₂) = 91%

Test 3 (T₃) = 88%

Test 4 (T₄) =?

AVERAGE = 90%

We can obtain the score of 4th test by doing the following:

AVERAGE = (T₁ + T₂ + T₃ + T₄) /4

90 = (83 + 91 + 88 + T₄) /4

90 = (262 + T₄) /4

Cross multiply

90 × 4 = 262 + T₄

360 = 262 + T₄

Collect like terms

360 – 262 = T₄

T₄ = 98%

Therefore, Sam need to score 98% in the 4th test in order to have an average score of 90%.