linear equation

Question

Suppose that you are taking a course that has 4 tests. The first three tests are for 100 points each and the fourth test is for 200 points. To get an B in the course, you must have an average of at least 80 percent on the 4 tests. Your scores on the first 3 tests were , , and . What is the minimum score you need on the fourth test to get an B for the course?.

Answer 1

Let's break this down.

To get a B in the course you need 80% average on all 4 tests, with the fourth test being worth double the previous tests - 200 points instead of 100.

The total possible number of points is 500 (100 for each of the first 3, and 200 for the 4th). What is 80% of that? 400 points.

Okay, so you need 400 points to get your B.

So far you have 247 points (77 + 81 + 89 points).

How many points do you still need? 400 - 247 = ???

Answer 2

the 200 point test is the same as two 100 point tests

so you basically have 5 100 point tests so you need 5*80=400 points

77+81+89+x=400

247+x=400

x=400-247

x=153

you need to get 153 points on the 200 point test

153/200=76.5

you need to get 76.5% on the last 200 point test