To estimate the total length of the wooden boards Nathan needs, we can round each of the lengths to the nearest whole number and then add them together.
- 16.45 feet can be rounded to 16 feet.
- 7.3 feet can be rounded to 7 feet.
- 12.8 feet can be rounded to 13 feet.
Now we can add these rounded values:
16 + 7 + 13 = 36 feet
Therefore, the closest estimate of the total length of wood Nathan needs is 36 feet.