Adding Mixed Measures
Adding mixed measures means combining measurements that use two different units, such as feet and inches or hours and minutes. Add the like units separately, then convert when the smaller unit exceeds its threshold (12 inches per foot, 60 minutes per hour). For 4 ft 9 in + 3 ft 7 in: 9 + 7 = 16 in = 1 ft 4 in, so total = 4 + 3 + 1 = 8 ft 4 in. This 7th grade Saxon Math Course 2 skill applies to carpentry, athletics, cooking, and any real-world context where measurements come in compound units.
Key Concepts
Property To add mixed measures, align the numbers to add the same units. Then, simplify the result when possible.
Examples 1 yd 2 ft 9 in. + 2 yd 1 ft 5 in. = 3 yd 3 ft 14 in., which simplifies to 4 yd 1 ft 2 in. 2 hr 30 min 40 s + 1 hr 40 min 35 s = 3 hr 70 min 75 s, which simplifies to 4 hr 11 min 15 s.
Explanation It’s like normal addition with a fun extra step! First, add each column of units together. Then, starting from the smallest unit on the right, simplify any large amounts by converting them into the next larger unit (like turning 70 seconds into 1 minute and 10 seconds).
Common Questions
How do you add mixed measures?
Add the smaller units together first. If the sum meets or exceeds the conversion threshold, carry over to the larger unit. Then add the larger units. For 4 ft 9 in + 3 ft 7 in: 16 in = 1 ft 4 in, total = 8 ft 4 in.
How many inches make a foot when adding mixed measures?
12 inches = 1 foot. So whenever inches sum to 12 or more, convert 12 inches to 1 foot and carry that foot to the feet column.
How do you add hours and minutes?
Add minutes first. If minutes reach 60 or more, convert 60 minutes to 1 hour and carry. Then add hours. For 2 hr 45 min + 1 hr 30 min: 75 min = 1 hr 15 min, total = 4 hr 15 min.
What grade learns to add mixed measures?
Adding mixed measures is a 7th grade skill in Saxon Math Course 2, applying both unit conversion knowledge and multi-column addition to practical measurement problems.
How is adding mixed measures like adding in different bases?
It is the same concept. Inches to feet is base-12; minutes to hours is base-60. Instead of carrying at 10 (like decimal), you carry at 12 or 60 respectively.
What is a common mistake when adding mixed measures?
Forgetting to carry the overflow. If inches sum to 15, you must record 1 ft 3 in — not 1 ft 15 in. Always apply the conversion when the smaller unit meets its threshold.