SOLUTION: A person's average was 64%. One the next test he got 68%. This raised his average to 65%. The next test, his average improved by 1% again. What did he get on the last test? I thou

Question 808437: A person's average was 64%. One the next test he got 68%. This raised his average to 65%. The next test, his average improved by 1% again. What did he get on the last test?
I thought of doing trial and error: I tried adding everything and dividing by the amount plus the number of extra 64s, but it took too long. I still don't know what the answer is. Please help me!
Answer by KMST(5328) (Show Source): You can put this solution on YOUR website!
We assume the 64% average was the average of tests.
THe sum of the grades of those tests was
.
When the next test grade was 68%, the sum of the grades of all the tests was
, and since there were tests by then,
the average was .
We are told that average was 65%, so
--> --> --> --> .
So the average was 64% after 3 tests and 65% after 4 tests.
After the 5th test, the average was 1% higher (than 65%),
so it was 65% + 1% = 66%.
The sum of the first 4 tests was
With a percentage score of on the fifth test,
the sum of the grades on the first 5 tests is

The average for the first 5 tests can be calculated as

and since the average is 66%,
--> --> --> -->

RELATED QUESTIONS
Richie's average on his math test was 64%. On the next test he had a mark of 76%, and... (answered by math_tutor2020)

After taking five tests, one student�s average grade is 65. Of the student scored 83 on... (answered by Fombitz)

Rick's average score on his first 3 test in math is 80. what must he score on the next... (answered by lynnlo)

Shauna had an English average of 84%. On her next test she scored 96%, and this raised... (answered by jorel1380)

Shauna had an English average of 84%. on her next test she scored 93%, and this raised... (answered by greenestamps)

Johns test scores are 95,90,83. What must he score on his next test to have an average... (answered by shweta)

Jay realizes he needs a mark of 100% on his next test in order to achive a 90%average for (answered by ankor@dixie-net.com)

Rick's average score on his three tests in math is 80.What must he score on the next test (answered by ewatrrr)

on teh first 6 tests of his spanish test, brandon got an average score of 85. What does... (answered by stanbon)