Core Connections Geometry, 2013
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Core Connections Geometry, 2013 View details
2. Section 10.2
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Exercise 81 Page 617

Practice makes perfect
a To sketch the spinner, we first need to use a compass to draw a circle. Open up the compass to an arbitrary length and draw the circle.
Use a straightedge to draw the circle's radius.

Next, place a protractor along the radius and measure a 60^(∘) angle.

Finally, we will draw a segment between the circles midpoint and the mark.

Having sketched a picture of the spinner, we should paint the bigger region blue and the smaller region red.

b The probability of landing on blue is the ratio of the blue region's central angle to 360^(∘).
P(blue)=300^(∘)/360^(∘)=5/6 According to the Multiplication Rule of Probability, we have to multiply the probability of landing on blue twice to obtain the probability of P(blue,blue).
P(blue,blue)=5/6* 5/6
Simplify right-hand side
P(blue,blue)=25/36
P(blue,blue)=0.694444
P(blue,blue)≈ 0.694
P(blue,blue)≈ 69.4 %
The probability of spinning blue twice is 69.4 %.
c To find the area of the sector we have to multiply the area of the spinner with the ratio of the sector's central angle to 360^(∘).

A=(7)^2π (300^(∘)/360^(∘)) = 128.28cm^2

d By multiplying the numerator and denominator of both probabilities so that the denominator equals 360^(∘), we can determine the central angle of each region.

P(purple)&=1/4 ⇔ P(purple)=90^(∘)/360^(∘) [1em] P(mauve)&=2/3 ⇔ P(mauve)=240^(∘)/360^(∘) The purple and mauve central angles occupy a total of 90^(∘)+240^(∘)=330^(∘). Since the spinner is 360^(∘), the green region must have a central angle of 30^(∘).