Mathematics
Grade 10
15 min
Round mixed numbers
Round mixed numbers
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1
Introduction & Learning Objectives
Learning Objectives
Round mixed number angle measures to the nearest whole degree.
Convert angle measures from degrees, minutes, and seconds (DMS) to a mixed number of degrees for rounding.
Round mixed number angle measures to a specified fractional part of a degree, such as the nearest half-degree.
Apply rounding rules to mixed number results in trigonometric calculations.
Justify the choice of rounding up or down based on the fractional part of an angle's measure.
Evaluate the impact of rounding on the precision of geometric calculations.
Ever tried to fit a shelf on a wall that wasn't perfectly square? 📐 A tiny error in an angle can make a big difference in the real world!
While you've rounded numbers before, this lesson focuses on a critical skill in geo...
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Key Concepts & Vocabulary
TermDefinitionExample
Mixed Number AngleAn angle measure consisting of a whole number of degrees and a proper fraction of a degree.An angle of 45 1/2° is a mixed number angle.
Rounding BenchmarkA reference point used to decide whether to round up or down. For rounding to the nearest whole number, the key benchmark for the fractional part is 1/2.To round 72 3/8°, we compare the fraction 3/8 to the benchmark of 1/2.
Degrees, Minutes, Seconds (DMS)A system for subdividing a degree of rotation, where 1 degree = 60 minutes (') and 1 minute = 60 seconds ("). This is often converted to a mixed number for calculation.An angle of 32° 15' 30" can be converted to 32 1/4° for easier rounding.
PrecisionThe level of detail in a measurement or calculation. Rounding a number reduces i...
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Core Formulas
Rounding Rule for Mixed Numbers (to the nearest whole)
Let the mixed number be $W \frac{n}{d}$. If $\frac{n}{d} \ge \frac{1}{2}$, round up to $W+1$. If $\frac{n}{d} < \frac{1}{2}$, round down to $W$.
Use this rule to approximate a mixed number angle to the nearest whole degree. To compare the fraction to 1/2, you can use cross-multiplication (e.g., for 3/7, compare 3*2 vs 7*1) or convert to decimals.
DMS to Mixed Number Conversion
Angle in Degrees = $D + \frac{M}{60} + \frac{S}{3600}$
To round an angle given in Degrees (D), Minutes (M), and Seconds (S), first convert it into a single value. This often results in a mixed number or a decimal that can be converted to one, which you can then round.
4 more steps in this tutorial
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Challenging
A precise angle measurement is 25° 29' 30". If this is rounded to the nearest whole degree for a calculation, what is the absolute error introduced by the rounding?
A.0.5083°
B.0.4917°
C.29.5°
D.0.0083°
Challenging
An angle is measured as 80° 45'. A student rounds this to the nearest whole degree for use in a formula. What is the approximate percentage error introduced by this rounding, relative to the original angle in decimal degrees?
A.1.25%
B.0.31%
C.0.92%
D.0.55%
Challenging
In a circle, an inscribed angle subtends an arc of 95° 33'. According to the inscribed angle theorem, the angle's measure is half the arc's measure. What is the measure of the inscribed angle, rounded to the nearest half-degree?
A.47.5°
B.48.0°
C.47.7°
D.47.0°
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