The ratio of the work output and work input-is called ____ of the machine.

Explanation

**Step-by-Step Solution:**

1. **Understanding Work Input and Work Output**:
- Work input refers to the amount of energy or work that is put into a machine to make it operate.
- Work output is the amount of work that the machine produces as a result of the work input.

2. **Defining the Ratio**:
- The ratio of work output to work input can be expressed mathematically as:
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