Find the mean of the first four test scores first.
(Add all numbers in set and divide by how many numbers there are)
81 + 87 + 71 + 89 = 328 / 4 = 82
Then, find the mean with the 85 added as the fifth term.
81 + 87 + 71 + 89 + 85 = 413 / 5 = 82.6
The impact that the 85 had on the mean test score was that the mean/average increased by 0.6.
You find the GCF of 250 and 363 by factoring. 250 = 5^4 * 2. 363 = 3 * 11^2, and they have no common factors, so 250/363 is already in its simplest form!
The last side would be 10