Answer
(a) 1Gm=1,000,000,000
(b) 0.000002500Gm
Work Step by Step
Since the prefix G means one billion, 1Gm is one billion meters.
A unit fraction is a fraction with a value of 1. 1Gm=1,000,000,000m, so $\frac{1Gm}{1,000,000,000m}$=1. This fraction can be used to convert m to Gm.
$2500m\times\frac{1Gm}{1,000,000,000m}.= 0.000002500Gm$