Mathematics Grade 10 15 min

Multiplication input/output tables: find the rule

Multiplication input/output tables: find the rule

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Introduction & Learning Objectives

Learning Objectives Analyze an input/output table to determine the constant multiplicative relationship representing a geometric dilation. Identify the scale factor 'k' for a dilation of a circle centered at the origin. Write the multiplication rule (e.g., r' = kr) that governs the relationship between an original circle's properties and its dilated image. Apply a determined multiplication rule to find the new coordinates of points on a dilated circle. Connect the algebraic concept of a multiplication rule to the geometric transformation of dilation. Use the multiplication rule to find the equation of a new circle after dilation. Ever wondered how animators make a cartoon sun grow bigger on screen? ☀️ They're using a mathematical 'rule' tha...
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Key Concepts & Vocabulary

TermDefinitionExample Input/Output TableA table that organizes pairs of related numbers. The 'input' is the starting value (e.g., original radius), and the 'output' is the resulting value after applying a specific rule (e.g., new radius).If the rule is 'multiply by 4', an input of 3 gives an output of 12. Multiplication RuleA rule for an input/output table where the output is found by multiplying the input by a single, constant number. In geometry, this constant is the scale factor.Output = 5 × Input DilationA geometric transformation that changes the size of a figure but not its shape or orientation. It is performed with respect to a fixed point, called the center of dilation.Using a photocopier to enlarge a picture of a circle to 150% of its original size....
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Core Formulas

Finding the Rule (Scale Factor) k = \frac{\text{Output}}{\text{Input}} To find the constant multiplier 'k' in a multiplication input/output table, divide any output value by its corresponding input value. In the context of circles, this could be new radius / original radius. Dilation of a Point (x', y') = (kx, ky) To find the coordinates of a point on a dilated image (x', y'), multiply the original coordinates (x, y) by the scale factor 'k'. This rule applies to every point on the circle. Dilation of a Circle's Radius r' = kr The radius of the dilated circle (r') is found by multiplying the original radius (r) by the scale factor 'k'.

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Sample Practice Questions

Challenging
The table shows the radius of an original circle (Input) and the Area of its dilated image (Output). Determine the multiplication rule for the radius, r' = kr.
A.r' = 2r
B.r' = 4r
C.r' = (4π)r
D.r' = 16r
Challenging
A circle A is dilated to create circle B using the rule from Table 1. Then, circle B is dilated to create circle C using the rule from Table 2. What single multiplication rule describes the dilation from circle A directly to circle C?
A.r_c = 2.5 r_a
B.r_c = 6 r_a
C.r_c = 8 r_a
D.r_c = 0.5 r_a
Challenging
The input/output table represents a single, consistent dilation of a circle's radius, but is missing two values, x and y. What is the value of x + y?
A.22.5
B.25
C.27.5
D.30

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