The two legs of a right triangle can serve as its base and its height. The area of the triangle is half the product of the two:

That is, the area is 3,000 square millimeters.

The area of a triangle is one half the product of its base and its height - in the above diagram, that means

.

Substitute , and solve for  :

To find the area of a triangle, multiply the base of the triangle by the height and then divide by two.

The area of the entire square is the square of the length of a side, or

.

The area of the white right triangle is half the product of its legs, or

.

Therefore, the area of that triangle is 

of that of the entire square.

The area of a triangle is half the product of its base and its height, so Mr. Jones's parcel originally had area 

 square meters.

The portion he sold his brother, represented by the red right triangle, has area

 square meters.

Therefore, the area of the parcel Mr. Jones retained is 

 square meters.

From this shape we are able to see that we have a square and a triangle, so lets split it into the two shapes to solve the problem. We know we have a square based on the 90 degree angles placed in the four corners of our quadrilateral. 

Since we know the first part of our shape is a square, to find the area of the square we just need to take the length and multiply it by the width. Squares have equilateral sides so we just take 5 times 5, which gives us 25 inches squared.

We now know the area of the square portion of our shape. Next we need to find the area of our right triangle. Since we know that the shape below the triangle is square, we are able to know the base of the triangle as being 5 inches, because that base is a part of the square's side. 

To find the area of the triangle we must take the base, which in this case is 5 inches, and multipy it by the height, then divide by 2. The height is 3 inches, so 5 times 3 is 15. Then, 15 divided by 2 is 7.5. 

We now know both the area of the square and the triangle portions of our shape. The square is 25 inches squared and the triangle is 7.5 inches squared. All that is remaining is to added the areas to find the total area. Doing this gives us 32.5 inches squared. 

Area of a triangle can be determined using the equation:

The area of a right triangle is half the product of the lengths of its legs, so we need to use the Pythagorean Theorem to find the length of the other leg. Set :

The legs are 15 and 20 inches long. Divide both dimensions by 12 to convert from inches to feet:

 feet

 feet

Now find half their product:

 square feet

The area of the entire rectangle is the product of its length and width, or

.

The area of the right triangle is half the product of its legs, or

The area of the green region is therefore the difference of the two, or

.

The green region is therefore

of the rectangle.

The area of the entire rectangle is the product of its length and width, or

.

The area of the right triangle is half the product of its legs, or

The area of the green region is therefore the difference of the two, or

.

The ratio of the area of the green region to that of the white region is 

That is, 11 to 4.