math · 30 minutes · Official OETT Aligned
Reading Measuring Tools
Inches, feet, tapes, and gap gauges
What to know
- feet and inches
- reading tape marks
- feeler gauge: thin blades that measure a gap
- changing units
Read the tool correctly, then use matching units for the calculation.
The core rule
Check the unit and the marks first. For stacked feeler-gauge blades, add their labeled thicknesses.
A feeler gauge uses thin blades to measure a small gap. If you stack blades, their thicknesses add together. For other measurements, change both amounts to the same unit before adding or subtracting. There are 12 inches in a foot.
Worked examples
Example 1: easy
2.5 feet = 30 inches.
- Convert 2.5 feet with 12 inches per foot: 2.5 × 12.
- The product is 30 inches; dividing 30 by 12 returns 2.5 feet.
Each foot contains 12 inches.
Example 2: medium
A .010-inch blade plus .006-inch blade measures .016 inch.
- Align the blade labels at thousandths: 0.010 + 0.006.
- Add every stacked thickness to obtain 0.016 inch.
Every blade adds to the thickness of the stack.
Example 3: hard
8 ft 7 1/2 in minus 2 ft 10 3/4 in equals 5 ft 8 3/4 in.
- Borrow one foot as 12 inches: 8 ft 7 1/2 in becomes 7 ft 19 1/2 in.
- Subtract 2 ft 10 3/4 in to get 5 ft 8 3/4 in.
Change one foot into 12 inches so you have enough inches to subtract.
Common mistakes
A stack of feeler blades reads only the thickest blade.
Add every blade in the stack. Each one takes up part of the gap.
Put it into practice
Use guided explanations, check your answers, and try a new variation.