Question

a) how long was this marathon in meters? how about decameters?

Explanation:

Step1: Define standard marathon length

A standard marathon is 42.195 kilometers.

Step2: Convert km to meters

Since $1\ \text{km} = 1000\ \text{m}$, calculate:
$42.195 \times 1000 = 42195\ \text{m}$

Step3: Convert meters to decameters

Since $1\ \text{decameter} = 10\ \text{m}$, calculate:
$\frac{42195}{10} = 4219.5\ \text{decameters}$

Answer:

The marathon is 42195 meters, or 4219.5 decameters.