Is this right can someone explain how to do this???
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Let us say distance between Eugenia's home and school is x miles.
Speed of Eugenia when she walked from home to school = 3 mph
Speed of Eugenia when she walked from school to home = 7 mph
Total time taken = 45 minutes or 0.75 hours
We know that the speed distance formula is given by:
Time taken by Eugenia when she walked from home to school = x/3 hours
Time taken by Eugenia when she walked from school to home = x/7 hours
Total time taken = x/3+x/7
So forming an equation we have,
Taking lcd of 7 and 3 as 21,
10x=15.75
Dividing both sides by 10 , we have
x= 1.575
Answer: So we can say that the distance between Eugenia's house and school is 1.575 miles.
Let X be the national sat score. X follows normal distribution with mean μ =1028, standard deviation σ = 92
The 90th percentile score is nothing but the x value for which area below x is 90%.
To find 90th percentile we will find find z score such that probability below z is 0.9
P(Z <z) = 0.9
Using excel function to find z score corresponding to probability 0.9 is
z = NORM.S.INV(0.9) = 1.28
z =1.28
Now convert z score into x value using the formula
x = z *σ + μ
x = 1.28 * 92 + 1028
x = 1145.76
The 90th percentile score value is 1145.76
The probability that randomly selected score exceeds 1200 is
P(X > 1200)
Z score corresponding to x=1200 is
z =
z =
z = 1.8695 ~ 1.87
P(Z > 1.87 ) = 1 - P(Z < 1.87)
Using z-score table to find probability z < 1.87
P(Z < 1.87) = 0.9693
P(Z > 1.87) = 1 - 0.9693
P(Z > 1.87) = 0.0307
The probability that a randomly selected score exceeds 1200 is 0.0307
now, by traditional method, as "x" progresses towards the positive infinitity, it becomes 100, 10000, 10000000, 1000000000 and so on, and notice, the limit of the numerator becomes large.
BUT, notice the denominator, for the same values of "x", the denominator becomes larg"er" than the numerator on every iteration, ever becoming larger and larger, and yielding a fraction whose denominator is larger than the numerator.
as the denominator increases faster, since as the lingo goes, "reaches the limit faster than the numerator", the fraction becomes ever smaller an smaller ever going towards 0.
now, we could just use L'Hopital rule to check on that.
notice those derivatives atop and bottom, the top is static, whilst the bottom is racing away to infinity, ever going towards 0.