Answer: 10%
Step-by-step explanation: I know that it's tempting to try do do percentage word problems in your head but this leads to a variety of careless mistakes. So I would advise always writing out the equation by simply reading the problem from left to right and solving it from there. That way you don't have to think about the problem at all until you get to your final answer.
So for this problem we have "what percent." It's important to understand to understand that percent means over 100 and "what" means x so "what percent" would be
. "of" means times, 20 is 20, "is" means equals, and 81 is 81.
.
We can rewrite this problem as
.
To get rid of the fraction, we multiply both sides by 100
and we have 20x = 200.
Dividing both sides by 20, you can use a calculator to find that x = 10.
Now let's check to see if our answer makes sense.
We have 10% of 20 is 2.
Well we know that 100% of 20 would be 20 so 10% of 36 should be a lot less than 20 so 10 seems to make sense.