Customary Units of Weight
Semester 4B · Chapter 10 · Lesson 3 · MATH-4B-C10-L03
Before you begin: prerequisite check
Recall: Division and mixed units. Attempt these questions independently first.
Convert 4 ft to in.
Show answer and reasoning
One ft = 12 in; 4×12=48.
Convert 7 mi to ft.
Show answer and reasoning
One mi = 5,280 ft; 7×5,280=36,960.
Convert 352 in to mixed yd and in.
Show answer and reasoning
Divide by 36: 9 groups and 28 leftover.
Key vocabulary
- metric unit
- meter, gram or liter family with decimal relationships
- customary unit
- inch, foot, pound or gallon family with its own conversion factor
- mixed units
- one measurement written using two units
- reference whole
- the full quantity of which a fraction is taken
Understand the concept
Weight in customary units can be expressed in pounds and ounces. One pound corresponds to sixteen ounces of weight. A package weighing two pounds and five ounces therefore weighs 2×16+5 = 37 ounces. Do not confuse an ounce of weight with a fluid ounce measuring liquid volume: they represent different properties. Use drawings of equal groups of 16 to exchange pounds and ounces. When a problem requires subtraction, convert to ounces first or regroup one pound as sixteen ounces before subtracting.
Fully worked examples and immediate checks
Read each example, predict how to begin, then follow its numerical explanation. The check below it is a fresh problem.
Worked example 1
How many ounces of weight are in 3 lb 12 oz?
Each pound weighs 16 ounces. 3×16+12=60.
Check 1: try it yourself
How many ounces of weight are in 8 lb 10 oz?
Show answer and reasoning
Each pound weighs 16 ounces. 8×16+10=138.
Worked example 2
How many ounces of weight are in 12 lb 12 oz?
Each pound weighs 16 ounces. 12×16+12=204.
Check 2: try it yourself
How many ounces of weight are in 3 lb 9 oz?
Show answer and reasoning
Each pound weighs 16 ounces. 3×16+9=57.
Worked example 3
Rename 185 oz as pounds and ounces.
185 = 16×11+9.
Check 3: try it yourself
Rename 93 oz as pounds and ounces.
Show answer and reasoning
93 = 16×5+13.
Guided practice
How many ounces of weight are in 9 lb 11 oz?
Show answer and reasoning
Each pound weighs 16 ounces. 9×16+11=155.
How many ounces of weight are in 11 lb 12 oz?
Show answer and reasoning
Each pound weighs 16 ounces. 11×16+12=188.
Rename 113 oz as pounds and ounces.
Show answer and reasoning
113 = 16×7+1.
One parcel is 6 lb 1 oz. A second is 7 lb 2 oz. How many total ounces of weight?
Show answer and reasoning
Convert each parcel to ounces of weight, then add: 97+114=211.
Explain why the word “ounce” in a grocery weight question must not automatically be treated as a fluid ounce.
Show answer and reasoning
A pound is grouped into 16 weight ounces; fluid ounces instead measure liquid capacity.
Independent practice
How many ounces of weight are in 2 lb 10 oz?
Show answer and reasoning
Each pound weighs 16 ounces. 2×16+10=42.
How many ounces of weight are in 8 lb 11 oz?
Show answer and reasoning
Each pound weighs 16 ounces. 8×16+11=139.
Rename 94 oz as pounds and ounces.
Show answer and reasoning
94 = 16×5+14.
One parcel is 8 lb 1 oz. A second is 9 lb 2 oz. How many total ounces of weight?
Show answer and reasoning
Convert each parcel to ounces of weight, then add: 129+146=275.
How many ounces of weight are in 9 lb 13 oz?
Show answer and reasoning
Each pound weighs 16 ounces. 9×16+13=157.
How many ounces of weight are in 11 lb 5 oz?
Show answer and reasoning
Each pound weighs 16 ounces. 11×16+5=181.
How many ounces of weight are in 10 lb 15 oz?
Show answer and reasoning
Each pound weighs 16 ounces. 10×16+15=175.
Rename 63 oz as pounds and ounces.
Show answer and reasoning
63 = 16×3+15.
Challenge and transfer
Use a diagram or verbal justification where appropriate. The goal is transfer rather than speed.
How many ounces of weight are in 7 lb 8 oz? Explain or sketch the mathematical relationship.
Show answer and reasoning
Each pound weighs 16 ounces. 7×16+8=120. State which quantities or geometric properties justify the method.
A learner claims: “An 8-ounce serving of juice has the same kind of ounces as half a pound of apples.” Identify what is wrong or incomplete and give a mathematically correct explanation.
Show answer and reasoning
False: liquid fluid ounces measure volume; ounces in a pound measure weight. The two cannot be substituted. Explain the relevant quantities or properties, not merely the final answer.
Exit check
How many ounces of weight are in 3 lb 10 oz?
Show answer and reasoning
Each pound weighs 16 ounces. 3×16+10=58.
How many ounces of weight are in 9 lb 7 oz?
Show answer and reasoning
Each pound weighs 16 ounces. 9×16+7=151.
Rename 203 oz as pounds and ounces.
Show answer and reasoning
203 = 16×12+11.
Mastery check: Solve a new instance without hints, explain why the method works, and return later to confirm retention.