Johnny has graded 20% of his 150 students papers how many papers does he still need to finish grading?

The correct answer is 120 papers.

First change 20% to a decimal 20% =.20

Then you multiply 150x. 20=30 to find out how many papers he has graded so far.

Then subtract 30 from 150 to find out how many papers he still needs to grade.

150 - 30 = 120

So he has 120 papers left to grade.