Suzette ran and biked for a total of 34 mi in 3.5 h. Her average running speed was 6 mph and her average biking speed was 12.5 mph. Let x = total hours Suzette ran. Let y = total hours Suzette biked. Use substitution to solve for x and y. Show your work. Check your solution. (a) How many hours did Suzette run? (b) How many hours did she bike?

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Answer:

From the information given

x is time for which she ran at speed of 6mi/h and

y is time for which she biked at speed of 12.5 mi/h

total time = 3.5 h

total distance = 34 mi

so

6x + 12.5y = 34 and

x + y = 3.5

x = 3.5 - y

6 ( 3.5 - y) + y = 34

6.5y = 13 which gives

y = 2 and this

x = 1.5

so suze ran for 1.5 h and biked for 2 h

CHECK

speed of run X time of run + speed of biking x time of biking must be = total distance covered

6 × 1.5 + 12.5 × 2 = 9 + 25= 34 mi

which is true

The speed of an object is the rate of distance traveled over time. Suzette ran for 1.5 hours, and she biked for 2 hours.

Given that:

[tex]Distance = 34mi[/tex]

[tex]Time = 3.5h[/tex]

Speed is calculated as:

[tex]Speed = \frac{Distance}{Time}[/tex]

Make Distance the subject

[tex]Distance = Speed \times Time[/tex]

Average running speed = 6 mph for x hours implies that:

[tex]Distance = 6 \times x[/tex]

[tex]Distance = 6x[/tex]

Average biking speed = 12.5 mph for y hours implies that:

[tex]Distance = 12.5 \times y[/tex]

[tex]Distance = 12.5y[/tex]

So, the total distance is:

[tex]Total = 6x + 12.5y[/tex]

The total distance is 34 miles. So, we have:

[tex]6x + 12.5y = 34[/tex]

The total time is 3.5h. So, we have:

[tex]x + y = 3.5[/tex]

Make x the subject

[tex]x = 3.5 - y[/tex]

Substitute [tex]x = 3.5 - y[/tex] in [tex]6x + 12.5y = 34[/tex]

[tex]6(3.5 - y) + 12.5y = 34[/tex]

[tex]21 - 6y + 12.5y = 34[/tex]

Collect like terms

[tex]- 6y + 12.5y = 34 - 21[/tex]

[tex]6.5y = 13[/tex]

Divide both sides by 6.5

[tex]y = 2[/tex]

Recall that:

[tex]x = 3.5 - y[/tex]

[tex]x = 3.5 - 2[/tex]

[tex]x = 1.5[/tex]

Hence, Suzette ran for 1.5 hours, and she biked for 2 hours.

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