Answer: 
Step-by-step explanation:
Given
Sample of 12 measurements has a mean of 16.5 and
a sample of 15 measurements has a mean of 18.6
Take 
be the mean and no of measurements
and 
be the mean and no of measurements in second case
Similarly,
Mean of 27 measurements
Answer:
Step-by-step explanation:
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Sure hope this helps you!
Answer:
8 months more
Step-by-step explanation:
first calculated how many months total she can donate: 8000/250 = 32 months
2 years has 24 months
subtract 32 with 24 which is 8 and that is how many months left that she can donate
Answer:
20
Step-by-step explanation:
"Nine out of ten students prefer math class over lunch. How many students would not prefer math class if 200 students were asked about their preferences, if they followed the same percentage?"
Nine out of ten
Change total (ten) to 200
Ratio: 9/10 = x/200
180/200 = x/200
x = 180 prefer math
200 - 180 = 20 do not prefer math
