Carol wanted to know about how much time students in her school spent surfing the Internet. So she asked 15 of her friends to complete a survey that she had prepared. Will the results of Carol’s survey represent the population of students in her school as a whole, and if so, which sampling method did Carol use? A. Yes, Carol used simple random sampling.
B. Yes, Carol used systematic random sampling.
C. Yes, Carol used stratified random sampling.
D. No, Carol’s survey was not a random sample.

D

Step-by-step explanation:

We can go through each form of sampling and see where this scenario fits.

- Simple random sampling is simply taking a random percentage of the population. In this case, with the population being students in Carol's school, this would entail taking a random sample from her school. As her friends are not randomly selected, this does not fit

- Systematic random sampling means that every nth item is selected. For example, if Carol took every 10th person at her school, this would fit. However, as her friends are not selected by Carol choosing every 5th or 10th person at school (or something like that), this does not fit.

- Stratified random sampling means that different subgroups of the population are selected, and once those are selected, it is randomized to see who out of the subgroup is selected. For example, if Carol took all the men and women in her school and chose 50 random men and 50 random women, this would work. Although Carol's friends may define a subgroup of the population here, she is not asking anyone outside of that subgroup here, so this does not fit.

As none of these fit, the only answer left is D

c.   x=2.4cm

step-by-step explanation:

similar triangles are triangles which have the same shape but not the same size. this means their angle measures are equal but their side lengths are not instead they are proportional. to solve, we will set up a proportion and solve.

a proportion is two equal ratios set equal to each other. we form the ratios by finding corresponding sides (sides which match to each other on both triangles by their position). out ratios will be one side of the small triangle over the corresponding side on the big triangle as shown below:

.

to solve the proportion, we'll cross multiply by multiplying numerator with denominator across the equal sign.

the first one is x^2+2x+2

the second one is x^2+4

the last one is x^2-4x+8