The scatter plot shows the relationship between the number of hours spent practicing piano per week and the number of pieces of
music the student can play:
A scatter plot is shown. The x-axis is labeled hours spent practicing and the y-axis is labeled number of pieces student can play. Data points are located at 1 and 1, 1 and 5, 2 and 10, 2 and 15, 3 and 15, 3 and 25, 4 and 40, 5 and 40, 5 and 50, 6 and 55, 6 and 70, 8 and 90, 3 and 70. A circle labeled T includes all points except for 3 and 70. Point 3 and 70 is circled and labeled as R.
Part A: What is the group of points labeled T called? What is the point labeled R called? Give a possible reason for the presence of point R. (3 points)
Part B: Describe the association between the number of hours practiced each week and the number of pieces a piano student can play. (2 points)
A scatter plot is shown. The x-axis is labeled hours spent practicing and the y-axis is labeled number of pieces student can play. Data points are located at 1 and 1, 1 and 5, 2 and 10, 2 and 15, 3 and 15, 3 and 25, 4 and 40, 5 and 40, 5 and 50, 6 and 55, 6 and 70, 8 and 90, 3 and 70. A circle labeled T includes all points except for 3 and 70. Point 3 and 70 is circled and labeled as R.
Part A: What is the group of points labeled T called? What is the point labeled R called? Give a possible reason for the presence of point R. (3 points)
Part B: Describe the association between the number of hours practiced each week and the number of pieces a piano student can play. (2 points)
1 answer:
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Refer to the figure shown below.
Because the maximum height of the parabola is 50 m, its equation is of the form
y = ax² + 50
This equation places the vertex at (0,50). The constant a should be negative for the vertex to be the maximum of y.
The base of the parabola is 10 m wide. Therefore the x-intercepts are (5,0) and (-5,0).
Set x=5 and y=0 to obtain
a(5²) + 50 = 0
25a = -50
a = -2
The equation of the parabola is
y = - 2x² + 50
At 2 m from the edge of the tunnel, x = 5 - 2 = 3 m.
Therefore the height of the tunnel (vertical clearance) at x = 3 m is
h = y(3)
= -2(3²) + 50
= - 18 + 50
= 32 m
Answer: 32 m
Because the maximum height of the parabola is 50 m, its equation is of the form
y = ax² + 50
This equation places the vertex at (0,50). The constant a should be negative for the vertex to be the maximum of y.
The base of the parabola is 10 m wide. Therefore the x-intercepts are (5,0) and (-5,0).
Set x=5 and y=0 to obtain
a(5²) + 50 = 0
25a = -50
a = -2
The equation of the parabola is
y = - 2x² + 50
At 2 m from the edge of the tunnel, x = 5 - 2 = 3 m.
Therefore the height of the tunnel (vertical clearance) at x = 3 m is
h = y(3)
= -2(3²) + 50
= - 18 + 50
= 32 m
Answer: 32 m