Complete question :
The 100m dah times in the girl's track meet were normally distributed with a mean of 13 seconds and a standard deviation of 0.3 seconds.
Lana finished the race in 13.2 seconds . If 84 other girls ran in the event, approximately how many runners did she beat?
Answer:
21 runners
Step-by-step explanation:
Mean, μ = 13 seconds
Standard deviation, σ = 0.3
Lana's race time = 13.2
We find the proportion of runners who had race time above 13.2 ;
Proportion of who had race tune above 13.2
P(x > 13.2)
Obtain the Zscore
Zscore = (x - μ) / σ
Z = (13.2 - 13) / 0.3
Zscore = 0.2 / 0.3 = 0.6667
P(Z > 0.6667) = 0.25239 (Z probability calculator)
This is about 0.25239 * 100 = 25.24% = 25% (nearest percent)
Hence, Number of runners Lana beat = 25% of total runners ;
0.25 * 84 = 21
Hence, Lana beat about 21 runners
Answer:
x = - 2, x = 7
Step-by-step explanation:
Given
f(x) = 4x² - 20x - 56
To find the zeros let f(x) = 0, that is
4x² - 20x - 56 = 0 ( divide through by 4 )
x² - 5x - 14 = 0 ← in standard form
(x - 7)(x + 2) = 0 ← in factored form
Equate each factor to zero and solve for x
x + 2 = 0 ⇒ x = - 2
x - 7 = 0 ⇒ x = 7
Answer:
The total surface area of a regular pyramidis the sum of the areas of its lateralfaces and its base. The general formula for thelateral surface area of a regular pyramidis where p represents the perimeter of thebase and SI the height of inclination.
The mean is 10.
To find the mean you add up all the numbers and divide by how many sets of numbers there were.
8+10+11+8+13=50
50/5=10.
