To estimate the total number of plates, you can multiply the number of racks by the number of plates per rack:
19 racks × 37 plates/rack.
For estimation, you can round these numbers. You could round 19 to 20 and 37 to 40:
20 racks × 40 plates/rack = 800 plates.
So, the correct estimate of how many plates are on the plate racks is 800.