Natalie answered 20% of the questions on a quiz incorrectly. If she answered 40 questions correctly, how many questions did she answer incorrectly?

Answer 1

Let she answered incorrectly x quations which 100% - 20 = 80%.

So x/0,2 = 40/0.8; x = 40·0.2/0.8 = 10

Answer 2

If we let "x" represent the total number of questions of the quiz, then "x-40" represents the number of questions answered incorrectly. We can use the 20% quantity and the "x-40" value to create a proportion and solve for the value of "x":

(20/100) = (x-40)/(x)

Cross-multiplying, we get (20)*(x) = (100)*(x-40), or 20x = 100x-4000.

Solving for "x", we get -80x = -4000, or x = 50, which means there are 50 total questions on the quiz.

Therefore, Natalie answered 50-40 = 10 questions incorrectly.