Put the cones in order from greatest volume to least volume.
(greatest on top)
Try to put them in order thinking about the formula instead of actually solving for the volume.
13 m, 5 m
9 cm, 12 cm
18 cm, 8 cm
8 cm, 3 cm
21 cm, 3 cm
21 cm, 3 cm
13 m, 5 m
18 cm, 8 cm
9 cm, 12 cm
8 cm, 3 cm