Neck: In 2/3 of an hour Naomi will stretch her neck one (there's not enough time for two neck stretches, that would require an hour).
Legs: In 2/3 of an hour, she will stretch her legs twice (1 stretch every 1/3 of an hour for 2/3 of an hour equals 2).
Arms: In 2/3 of an hour she will stretch her arm four times (2/3 divided by 1/6 equals 4).
Total stretches: 1 neck stretch, 2 legs stretches, and 4 arms stretches.
the correct answer is a^6
Answer:
The number is 8 because 
And if you add 4, you get 20
Hence, the number is 8
The 68-95-99.7 rule tells us 68% of the probability is between -1 standard deviation and +1 standard deviation from the mean. So we expect 75% corresponds to slightly more than 1 standard deviation.
Usually the unit normal tables don't report the area between -σ and σ but instead a cumulative probability, the area between -∞ and σ. 75% corresponds to 37.5% in each half so a cumulative probability of 50%+37.5%=87.5%. We look that up in the normal table and get σ=1.15.
So we expect 75% of normally distributed data to fall within μ-1.15σ and μ+1.15σ
That's 288.6 - 1.15(21.2) to 288.6 + 1.15(21.2)
Answer: 264.22 to 312.98
