Question

If tashi scores an 85, 87, and 89 on his first three tests, what must he score on his fourth test so that the average of the four test scores is exactly 90?

Answer 1

Tashi must score 99 on his fourth test to have an average of 90.

Step-by-step explanation:

To find out what Tashi must score on his fourth test to have an average of 90, we can use the formula for calculating the average. The average of four test scores is the sum of the scores divided by 4. So, to have an average of 90, the sum of all four scores must be (4 * 90) = 360.

Given that Tashi scored 85, 87, and 89 on his first three tests, we can subtract these scores from the target sum to find out what he needs to score on his fourth test:

(85 + 87 + 89 + x) / 4 = 360

Combine like terms and solve for x:

261 + x = 360

x = 360 - 261

x = 99

Tashi must score 99 on his fourth test to have an average of 90.

Answer 2

 The possible score that he must make is a 9