Which ratio yields the highest output speed relative to input?

• A. 2:1
• B. 1:1
• C. 0.67:1
• D. 0.25:1

Answer: (C)

In a simple gear pair, the output speed relative to input depends on the gear teeth ratio: ω_out/ω_in = N_in/N_out. A larger ratio means the output spins faster. The setup where the input gear has twice as many teeth as the output (a 2:1 ratio) makes the output run at double the input speed, which is the highest among the given options. A 1:1 ratio gives the same speed, while 0.67:1 and 0.25:1 reduce the output speed to about two-thirds and one-quarter of the input, respectively. So the fastest output occurs with the 2:1 arrangement.