Esther starts at one corner of a square field and walks 90 feet along one side to another corner of the field. she turns 90° and walks 70 feet, and then walks straight back to where she started. what is the area of the part of the field she walked around?
a. 3150 ft²
b. 4900 ft²
c. 6300 ft²
d. 8100 ft²

Since it is a square field and she walked from one corner to another, each side of the square filed is 90 feet.
Since she walked 70 feet and then straight back to where she started, she has formed a triangle, the legs are 90 and 70 and the hypotenuse (the distance back to the start) is not needed to solve this problem.
So we have a triangle whose length is 90 and whose height is 70
A =  bh  or in this case  (90) x (70) or 1/2 of 6300.  Answer a.  3150 ft² is half of 6300 and is the correct answer