🔍 Key Concepts

• Relationship between gear teeth and RPM (speed ratio N1/N2 = T2/T1 for meshed gears) • How a compound gear works when two gears (B and C) are on the same shaft and therefore have the same RPM • Overall gear train ratio from A through B/C to D

💭 Think About

• First, write the speed relationship between gear A and gear B using their tooth counts. Which gear is the driver? • Since gears B and C are fixed on the same shaft, what does that tell you about the RPM of C compared with B? • Use the RPM of C to find the RPM of D. Then simplify the overall ratio from A to D to check your math.

✅ Before You Answer

• Be sure you are using the correct formula: for two meshed gears, driver RPM × driver teeth = driven RPM × driven teeth • Confirm you have treated B and C as same RPM (compound gear) and only changed RPM again when going from C to D • After computing, see if you can simplify the complete ratio from A to D in one step using (teeth of driven ÷ teeth of driver) for each mesh, multiplied together, to verify your final choice