Page 135 - Math Course 3 (Book 1)

Slope-Intercept Form Equations

MO. 4 - L3b Find the ideal maximum heart rate for a
55-year-old person exercising to burn fat.
Slope-Intercept Form:

Real World Data The age 55 is 30 years older than 25. So, a = 30.

3
R = – a + 117 Ideal heart rate equation
5
Let’s Begin R = – (30) + 117 Replace a with 30.
3
5
R = 99 Simplify.

Real World Example The ideal heart rate for a
Answer 55-year-old person is 99 beats
HEALTH per minute
The ideal maximum heart rate for a 25-year-old
exercising to burn fat is 117 beats per minute. For every
5 years older than 25, that ideal rate drops 3 beats per
minute. Write a linear equation to find the ideal maximum Your Turn!
heart rate for anyone over 25 who is exercising to burn
fat. Real World Example

ideal The amount of money spent on Christmas
years rate gifts has increased by an average of $150,000
rate older for ($0.15 million) per year since 1986. Consumers
Ideal of than 25 year spent $3 million in 1986. Write a linear equation
Words rate equals change time 25 plus old to find the average amount spent for any year

since 1986.
Variables Let R = the ideal heart rate.
Let a = years older than 25. A. D = 0.15n
B. D = 0.15n + 3
3 C. D = 3n
Equation R = – × a + 117 D. D = 3n + 0.15
5
3
R = – a + 117
5
Answer where R is the ideal heart rate and a is Answer
the number of years older than 25.

Graph the equation.
3
The graph passes through (0, 117) with a slope of – 5

Answer

Ideal Heart Rate
Maximum Heart Rate 116 R = – a + 117
117
3
5
115
114
113
112

0 1 2 3 4 5 6 7 8
Years Above 25

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