Mathematics
Grade 11
15 min
Multiply one-digit numbers by three-digit numbers
Multiply one-digit numbers by three-digit numbers
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1
Introduction & Learning Objectives
Learning Objectives
Calculate the measure of a coterminal angle by multiplying 360° by a one-digit integer representing the number of rotations.
Determine the arc length of a circle by multiplying a three-digit radius by a one-digit central angle in radians.
Compute the area of a circular sector where the calculation involves multiplying a three-digit number (derived from the radius squared) by a one-digit central angle.
Apply the Law of Sines to find a missing side length when it requires multiplying a three-digit side length by a one-digit scalar.
Solve for total angular displacement by multiplying a three-digit angular velocity by a one-digit time interval.
Accurately perform the multiplication of a one-digit number by a three-digit number as a critical step within complex...
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Key Concepts & Vocabulary
TermDefinitionExample
Coterminal AnglesAngles in standard position (vertex at the origin, initial side on the positive x-axis) that have the same terminal side. They are found by adding or subtracting integer multiples of 360° or 2π radians.An angle of 450° is coterminal with 90° because 450° = 90° + 360° × 1. The multiplication step is 360 × 1.
Arc Length (s)The physical distance along the curved line making up an arc. The calculation requires the central angle to be in radians.For a circle with a radius of 150 meters and a central angle of 3 radians, the arc length is s = 150 × 3 = 450 meters.
Sector Area (A)The area of the portion of a circle enclosed by two radii and their intercepted arc. The calculation requires the central angle to be in radians.For a circle with a radius of 20 ft...
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Core Formulas
Coterminal Angle Formula (Degrees)
\theta_{coterminal} = \theta + 360^\circ \times n
Use this formula to find a coterminal angle, where 'θ' is the given angle and 'n' is an integer representing the number of full rotations. The core multiplication is 360 × n.
Arc Length Formula
s = r \times \theta
Calculates the arc length 's' of a circle with radius 'r' and a central angle 'θ' measured in radians. The core multiplication is r × θ.
Sector Area Formula
A = \frac{1}{2} r^2 \theta
Calculates the area 'A' of a circular sector with radius 'r' and a central angle 'θ' measured in radians. The multiplication often involves a three-digit number (from r²) and a one-digit number (θ).
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Challenging
A satellite in a circular orbit has an angular velocity of 125 milliradians per second. After 8 seconds, it has traveled an arc length of 800 km. What is the radius of its orbit in kilometers?
A.100 km
B.800 km
C.1000 km
D.6400 km
Challenging
An angle θ is coterminal with 40° and is found by making 5 full counter-clockwise rotations. This angle θ (in radians) is then used to find the arc length on a circle with a 100-unit radius. What is that arc length? (Use π ≈ 3.14)
A.1840 units
B.3211 units
C.1800 units
D.70 units
Easy
Which formula is used to calculate the arc length 's' of a circle with radius 'r' and a central angle 'θ' in radians?
A.= (1/2)r²θ
B.θ_coterminal = θ + 360° × n
C.s = r + θ
D.s = r × θ
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