I just took the test the correct answer is 285.74 square centimeters
There are 4 pairs of overlapping triangles that I can see that are congruent. Two pairs share vertically opposite angles.
One more pair have right angles at the bottom of the rectangle.
One other pair have right angles at the top of the rectangle.
Answer:

Step-by-step explanation:
we know that
The formula to find the sum is equal to

where
a1 is the first term
an is the last term
n is the number of terms
In this problem we have



substitute the values in the formula

TO get the decimal 8 is obviously 8.0 and for 21/40 just divide 40 for both the numerator and denominator. Then add the 8.0 with the answer you get for 40 together to get the final answer.