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yarga [219]
3 years ago
11

On Saturday morning, Ahmed decided to take a bike ride from one end of the 15-mile bike trail to the other end of the bike trail

and back. His average speed the first half of the ride was 2 mph faster than his speed on the second half. Find an expression for Ahmed's total travel time. If his average speed for the first half of the ride was 12 mph, how long was Ahmed's bike ride? ​
Mathematics
1 answer:
frosja888 [35]3 years ago
3 0

The expression which relates the total time taken and the time taken for the trip is [15s + 15(s+2)] / s² + 2s and 2.32 hours respectively.

<em>Travel time = distance ÷ speed </em>

<u>Second half of the trip</u> :

  • <em>Speed = s mph</em>

  • <em>Distance covered = 15 miles</em>

<u>Time taken for second half of trip</u> :

Time taken = 15 / s

<u>First half of the trip</u> :

  • <em>Speed = s + 2 mph </em>

<u>Time taken for first half of trip :</u>

Time taken = 15 / (s+2)

<u>Total time taken :</u>

<em>First half + second half</em>

15/(s+2) + 15/s = [15s + 15(s+2)] / s² + 2s

B)

If s = 12

<em>Substitute s = 12 into the expression</em> :

[15(12) + 15(12+2)] / 12² + 2(12)

[180 + 210] / 144 + 24

390 / 168

= 2.32 hours

Therefore, the total time taken is 2.32 hours.

Learn more : brainly.com/question/18796573

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In Triangle XYZ, A is the midpoint of XY, B is the midpoint of YZ, and C is the midpoint of XZ.
Roman55 [17]

The perimeter of triangle ABC is 24 units

Step-by-step explanation:

If a segment joining the mid points of two sides of a triangle, then

this segment is:

  • Parallel to the third side
  • Its length is half the length of the third side

In The triangle XYZ

∵ A is the mid point of XY

∵ B is the mid point of YZ

∴ AB = \frac{1}{2} XZ

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- Substitute the value of XZ in AB

∴ AB = \frac{1}{2} × 18 = 9 units

∵ B is the mid point of YZ

∵ C is the mid point of XZ

∴ BC = \frac{1}{2} XY

∵ AY = 7 units

∵ AY = \frac{1}{2} XY

∴ XY = 2 × AY

∴ XY = 2 × 7

∴ XY = 14 units

∴ BC = \frac{1}{2} × 14 = 7 units

∵ A is the mid point of XY

∵ C is the mid point of XZ

∴ AC = \frac{1}{2} YZ

∵ BZ = 8 units

∵ BZ = \frac{1}{2} YZ

∴ YZ = 2 × BZ

∴ YZ = 2 × 8

∴ YZ = 16 units

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∵ The perimeter of a triangle = the sum of the lengths of its sides

∴ Perimeter Δ ABC = AB + BC + AC

∴ Perimeter Δ ABC = 9 + 7 + 8 = 24 units

The perimeter of triangle ABC is 24 units

Learn more:

You can learn more about triangles in brainly.com/question/5924921

#LearnwithBrainly

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A normally distributed set of numbers has a mean of 75 and a standard deviation of 7.97. What percentage of values lies between
lana [24]

Answer:

63% of the values lies between 70 and 85.

Step-by-step explanation:

We are given that a normally distributed set of numbers has a mean of 75 and a standard deviation of 7.97.

<em>Let X = Set of numbers</em>

The z-score probability distribution for is given by;

                Z = \frac{  X -\mu}{\sigma}  ~ N(0,1)

where, \mu = mean value = 75

            \sigma = standard deviation = 7.97

The Z-score measures how many standard deviations the measure is away from the mean. After finding the Z-score, we look at the z-score table and find the p-value (area) associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X.

So, percentage of values that lies between 70 and 85 is given by = P(70 < X < 85) = P(X < 85) - P(X \leq 70)

   P(X < 85) = P( \frac{  X -\mu}{\sigma} < \frac{  85-75}{7.97} ) = P(Z < 1.25) = 0.89435  {using z table}

   P(X \leq 70) = P( \frac{  X -\mu}{\sigma} \leq \frac{  70-75}{7.97} ) = P(Z \leq -0.63) = 1 - P(Z < 0.63)

                                                 = 1 - 0.73565 = 0.26435

<em>Now, in the z table the P(Z </em>\leq<em> x) or P(Z < x) is given. So, the above probability is calculated by looking at the value of x = 1.25 and x = 0.63 in the z table which has an area of 0.89435 and 0.73565 respectively.</em>

Therefore, P(70 < X < 85) = 0.89435 - 0.26435 = 0.63 or 63%

<em>Hence, 63% of the values lies between 70 and 85.</em>

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Step-by-step explanation:

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