Answer: 170
Step-by-step explanation: 170x90% (0.9) = 153
Answer: I believe the standard deviation will remain the same, 6, choice A.
Step-by-step explanation: Standard deviation is calkculated based on the difference of each point from the mean. If 10 were added to each score, the mean would also increase by 10. That would mean that the difference between the mean and each score would be exactly the same, leading to an identical standard deviation. Sounds crazy, but that's what numbers do for a living.
Answer:
C. 2.0 < t < 2.5
Step-by-step explanation:
time = distance / speed
The circumference of the lake is given by ...
C = πd = 2π miles ≈ 6.28 miles
Then Johanna's time is ...
(6.28 mi)/(3 mi/h) ≈ 2.09 h
This time is in the interval (2, 2.5), so matches choice C.
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<em>Alternate solution</em>
If we take pi to be 3, then this boils down to ...
2×3/3 = 2 . . . hours
Pi is on the order of 5% more than 3, so her time will be on the order of 5% more than 2 hours, or just above 2, but not as great as 2.5 hours. This sort of estimating can get you to the correct answer without a calculator.
-3/5 = -6/10
9/10 - 6/10 = 3/10
