jmc

First, convert one billion meters to kilometers.

$$1000000000\text{ meters}\cdot \frac{1\text{ kilometer}}{1000\text{ meters}}=1000000\text{ kilometers}$$

Next, we divide the total distance traveled by the circumference around the Earth to get the total number of trips around the world, or $\frac{1000000}{40000}=\boxed{25}$ trips.