Answer: A rain gauge measures the amount of rainfall based off of the amount collected in the cylinder.
Step-by-step explanation: A rain gauge is really just a cylinder that catches rain. If an inch collects in the cylinder, it means an inch of rain has fallen. It's that simple. Most standard rain gauges have a wide funnel leading into the cylinder and are calibrated so that one-tenth of an inch of rain measures one inch when it collects inside.