Answer:
They can either decrease the confidence level or increase the sample size, that is, survey more students.
Step-by-step explanation:
The width of a confidence interval is given by:
In which z is the critical value correponding to the confidence level(higher confidence level, higher z is), 
is the standard deviation of the population and n is the size of the sample.
The students realize that this interval contains a large margin of error. What can they do to make a narrower interval?
Looking at the formula for M, they can either decrease the confidence level or increase the sample size, that is, survey more students.
Answer:
15.
16. 10 ml of 20% saline and 40 ml of 10% saline
Step-by-step explanation:
A chemist takes x ml of 20% saline and y ml of 10% saline. In total, he takes
x + y ml that is 50 ml, so
There are 
ml of salt in x ml of 20% saline and 
ml of salt in 10% saline. There are 
ml of salt in 50 ml of 12% saline. Thus,
15. We get the system of two equations:
16. Solve this system. From the first equation:
Substitute it into the second equation:
Answer:
34
9 + 25
Step-by-step explanation:
Step 1: Define expression
a² + b²
a = 3
b = 5
Step 2: Substitute
3² + 5²
Step 3: Evaluate
9 + 25
34
