So there are seven days. Of course, if you just add up

200

100

50

25

12.5

6.25

3.125

You'll get about 397.

The way to do this is with the sum

When n is the number of terms, and the a's are the first and last terms.

So we have n = 7

a_1 = 200

a_n = a_7 = 3.125

Compute.