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## MAP Recommended Practice

### Unit 8: Lesson 2

Area and circumference challenge problems

# Area of a shaded region

Here's a fun one: find the area of a shaded region where you first determine the area of a square and then the area of a circle. Created by Sal Khan.

## Want to join the conversation?

• This may not sound very smart but why did you multiple 3*3
• Sal multiplied 3 and 3 because the formula for getting area is A = r^2 pi. If our radius is 3, and if part of the formula is r^2, to get the radius to the second power you multiply 3 and 3 .
• at what was that green thing
• It is due to an incomplete answer. Once you finish typing your answer, assuming it is an acceptable form for the particular question, the green guy goes away:)
• Why he didn't multiply it by 4 like:
100 - 4(3^2)pi? isn't this going to give us all four sides? o.O #confused

PS: Oh I get it, I get it now :D. (3^2)pi will give us the entire area of full circle :D
• What if your book doesn't give the area of the shape?
• Why don't you multiply by four at the end instead of just 9π? Aren't you solving for four sides then subtracting?
• find the area of shaded region of square 6cm
• So wait, in this situation, how could u have found the area of the shaded region with the diametrr or is there no possible way?
• Find the shaded area of a triangle
(1 vote)
• Area of a triangle is base times the height and then divide the base times the hight by 2. for example a triangle with a base of 3 and a height of 5 would have an area of 7.5.