Question 687686: Ted needs an average of at least 70 on his three history tests. He has already scored 85 and 60 on two tests. What is the minimum grade Ted needs on his third test
Answer by josh_jordan(263)   (Show Source):
You can put this solution on YOUR website! To solve, we first need to know how to find the average of a group of numbers. To find the average of a group of numbers, you add all the numbers together and divide that answer by the number of numbers you have. For instance, to find the average of 1, 2, 3, 4 and 5, we would add all the numbers together, which would equal 15. We would then divide that number by 5, because there are 5 numbers total: 15/5 = 3. So the average is 3.
Now, to find the average in your problem, we need to look at what we know:
He received an 85 and 60 on two of the test scores
He needs an overall average of 70
Let's set this up in equation form:
Now, let's get rid of our fraction on the left. We can do this by multiplying the entire equation by 3, giving us:
85 + 60 + x >= 210
Next, combine the numbers on the left, which will give us:
145 + x >= 210
Finally, subtract 145 from both sides, which will give us our answer:
145 + x - 145 >= 210 - 145 =
x >= 65
So, in order to average at least 70, he must score a 65 or higher on his third test.
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