Empirical rule (statistics)Help please!!!
1 answer:
The empirical rule you're referring to is the 68-95-99.7 rule, which asserts that for a normal (bell-shaped) distribution, approximately 68% of the distribution lies within 1 standard deviation of the mean; 95% lies within 2 standard deviations of the mean; and 99.7% lies within 3 standard deviations of the mean.
Let be the random variable denoting vehicle speeds along this highway. We want to find
. To use the rule, we need to rephrase this probability in terms of the mean and standard deviation.
Notice that , and
. In other words, 61 and 79 both lie exactly 3 standard deviations away from the mean, so
.
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Cost of each bags of flour = $2.50
Cost of each bags of butter = $3.75
Solution:
Let f be the bags of flour and b be the pounds of butter.
Cost of 20 bags of flour 16 pound of butter = 110
⇒ 20f + 16b = 110 -------------------- (1)
Cost of 30 bags of flour 12 pound of butter = 120
⇒ 30f + 12b = 120 -------------------- (2)
Equation (1) and (2) are the system of equations.
(2) ⇒ 30f + 12b = 120
Subtract 30f from both sides.
⇒ 12b = 120 – 30f
Divide by 12 on both sides.
-------------------- (3)
Substitute (3) in (1).
Subtract 160 from both sides.
Divide by –20, we get
f = 2.50
Substitute f = 2.5 in equation (3), we get
b = 3.75
Cost of each bags of flour = $2.50
Cost of each bags of butter = $3.75