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ASVAB · Simple Machines (Levers, Pulleys, Gears)

A small gear with 10 teeth drives a large gear with 30 teeth. For every 3 turns of the small gear, the large gear turns:

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Correct answer

1 time

  1. A 30 times
  2. B 1 time
  3. C 9 times
  4. D 3 times

Why this is the answer

The large gear turns 1 time. ASVAB Mechanical Comprehension tests gear ratios. The gear ratio = driven gear teeth ÷ drive gear teeth = 30 ÷ 10 = 3:1. This means the small (drive) gear must turn 3 times for the large (driven) gear to turn ONCE. So for 3 turns of the small gear, the large gear turns 3 ÷ 3 = 1 time. The larger gear turns SLOWER (fewer rotations) but with more torque. Calculating gear rotations from tooth counts is commonly tested.
Source: ASVAB Mechanical Comprehension — Gear Ratios

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About this topic: Simple Machines (Levers, Pulleys, Gears)

Simple machines — levers, pulleys, gears, inclined planes, wheel-and-axle, screws — are the heart of Mechanical Comprehension. Each question comes down to mechanical advantage: how much the machine multiplies force, and the trade-off in distance. This is one of 23 Mechanical Comprehension questions on simple machines (levers, pulleys, gears), each with a full explanation on a single study page.

New to this exam? Our ASVAB exam guide explains the format, scoring, and how to prepare.

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