Answer:
m∠ABD = 88º
m∠CBD = 23º
Step-by-step explanation:
(-10x + 58) + (6x + 41) = 111
Combine like terms
-4x + 99 = 111
Subtract 99 from both sides
-4x = 12
Divide both sides by -4
x = -3
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m∠ABD = -10x + 58
m∠ABD = -10(-3) + 58
m∠ABD = = 30 + 58
m∠ABD = 88º
m∠CBD = 6x + 41
m∠CBD = 6(-3) + 41
m∠CBD = -18 + 41
m∠CBD = 23º
Let's call our estimate x. It will be the average of n IQ scores. Our average won't usually exactly equal the mean 97. But if we repeated averages over different sets of tests, the mean of our estimate the average would be the same as the mean of a single test,
μ = 97
Variances add, so the standard deviations add in quadrature, like the Pythagorean Theorem in n dimensions. This means the standard deviation of the average x is
σ = 17/√n
We want to be 95% certain
97 - 5 ≤ x ≤ 97 + 5
By the 68-95-99.7 rule, 95% certain means within two standard deviations. That means we're 95% sure that
μ - 2σ ≤ x ≤ μ + 2σ
Comparing to what we want, that's means we have to solve
2σ = 5
2 (17/√n) = 5
√n = 2 (17/5)
n = (34/5)² = 46.24
We better round up.
Answer: We need a sample size of 47 to be 95% certain of being within 5 points of the mean
6. Answer:
72.84
Step-by-step explanation:
To find the perimeter of the rectangle, just add the sides together except the one connected to the semicircle
12 + 15 + 15 = 42
The diameter of the semi circle is 12
πr + d = 6 * π + 12 ≈ 30.84
Add them together
42 + 30.85 = 72.84
7. Answer:
78.54
(78.5)
Step-by-step explanation:
The shape is a circle
Radius is 5
Diameter is 10 (diameter is always double of the radius)
π * r^2 = π * 25 cm^2 = 78.54 cm^2
8. Answer:
50.27
Step-by-step explanation:
The shape is a circle
Radius is 4
Diameter is 8 (diameter is always double of the radius)
π * r^2 = π * 16 ft^2 = 50.27 ft^2
(16 = 8 * 2)
