Topic: Machine Design
For a gear pair, the center distance is 200 mm, and the module is 5 mm. The sum of teeth in the gear pair is:
- A. 40
- B. 80
- C. 60
- D. 100
Answer: B. 80
Explanation: Center distance $C$ for a gear pair is the sum of their pitch radii: $C = \frac{d_1 + d_2}{2}$.
Since pitch diameter $d = m \times T$ (where $m$ is module and $T$ is number of teeth):
$C = \frac{m T_1 + m T_2}{2} = \frac{m(T_1 + T_2)}{2}$.
$200 = \frac{5 \times (T_1 + T_2)}{2}$.
$400 = 5(T_1 + T_2) \Rightarrow T_1 + T_2 = \frac{400}{5} = 80$.