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love history [14]
4 years ago
12

A study is conducted to determine if the blue light from a tablet device will affect the fall asleep time of people in various a

ge groups differently. Volunteers for the study are grouped by age: 18-30, 31-50, and 50. Half of each group is assigned a standard tablet, the other half is assigned a tablet with reduced blue light. People in each group are asked to use the tablet for 10 minutes before bed and their fall asleep time is recorded. Which of the following is correct?
a. Blocks: the three age groups. Treatments: using the standard tablet or the reduced blue light tablet before bed. Response variable: How the eyes react to blue light.
b. Blocks: the three age groups. Treatments: measuring how long it takes to fall asleep. Response variable: The hours of sleep recorded.
c. Strata: the three age groups. Treatments: using the standard tablet or the reduced blue light tablet before bed. Response variable: How the eyes react to blue light.
d. Blocks: the three age groups. Treatments: using the standard tablet or the reduced blue light tablet before bed. Response variable: Time it takes to fall asleep.
e. Blocks: the group receiving the standard tablet and the group receiving the reduced blue light tablet. Treatments: using the standard tablet or the reduced blue light tablet before bed. Response variable: Time it takes to fall asleep.
Mathematics
1 answer:
stepan [7]4 years ago
6 0

Answer: (d) Blocks: the three age groups. Treatments: using the standard tablet or the reduced blue light tablet before bed. Response variable: time it takes to fall asleep

Step-by-step explanation:

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<em>They took 101 peaches to market.</em>

<u>Check:</u>

In the 1st hour, they sold (101/2 + 1/2) = 102/2 = 51.  They had 50 left.

In the 2nd hour, they sold (50/3 + 1/3)=51/3=17.  They had (50-17)=33 left.

In the 3rd hour, they sold (33/4 + 3/4) = 36/4 = 9.  They had (33-9) = 24 left.

In the final hour, they sold (24/5 + 1/5) = 25/5 = 5.  They had (24-5) = 19 left.  yay!

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The key to solving this one is to work it backwards.

-- They had 19 peaches left at the end of the day.

-- During the final hour, the 1/5 of a peach that they sold left them with 19,
so they had 19-1/5 before they sold the 1/5 of a peach.
The 19-1/5 was 4/5 of what they had at the beginning of the final hour.
So, at the beginning of the final hour, they had (5/4)x(19.2) = 24 .

-- During the 3rd hour, the 3/4 of a peach that they sold left them with 24,
so they had 24-3/4 before they sold the 3/4 of a peach.
The 24-3/4 was 3/4 of what they had at the beginning of that hour.
So, at the beginning of the 3rd hour, they had (4/3)x(24.75) = 33 .

Do the same for the 2nd hour.

Then do the same for the 1st hour.

And you'll work your way back up to 101 peaches.


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