Rather than search the internet for websites, I looked for iPad apps and found at least two free ones to review.

The first app is by Wasabi Applications and its called Area Quiz. The idea behind this game is that you are given a figure with missing information. Using logic, you determine the missing value but the value might be the whole area, part of the area, or a side measurement. The problems are not always easy.

When you turn on the app, this is the screen that appears. Notice the unit is cm^2 because this app was created by a company that uses metric. Once you tough the play button you are taken to the second screen.

The second screen indicates there are 5 different levels to work through. You cannot move to another level until you have acquired a certain number of stars. Note its only 10 to unlock level 2 but it increases with each level so it requires additional work.

I am on level one number three. Note the picture, you are expected to find the area of the shaded part. It requires thought to figure out the two missing measurements. You type in the answer and hit enter.

If your answer is correct, you get a start and move on. If it is wrong, a huge red X appears and you cannot move on till you get the correct answer.

The other app is Area Maze marketed by Happy Meals which is just as good but some of the problems are a bit trickier.

This is the front screen when you open up the app. Notice much is in Japanese but the directions and numbers are in English.

As
far as I can tell, there may be more levels but I have not worked my
way through this. I got as far as number eight before I got stuck.
When you do it and you are correct, you get a beautiful green area but
if you are wrong, it plants a huge red X and tells you to try again.

This
is the one I am stuck on. This app varies from the other because of
the timer that ticks away as you work on the problem. As I was writing
this, I realized I was looking at the whole thing from the wrong angle.
I checked my answer and I was right! Yeah.

I
plan to put these apps on my iPads. When they work the problems, I am
going to require they sketch out the problem and show how they solved
it. This gives them a chance to practice explaining because many of the
new tests require they show their thinking.

Check them out, they are both free.