Answer:
Is an experimental study
Step-by-step explanation:
In an observational study you don't control any aspect of the investigation you just observe the variables that you determined since the beginning without any intervention.
In this case you are controlling who sees one or the other video, then you are controlling one of the variables that is the type of video each group sees and because of this it is an experimental study. Researchers designed an experiment to prove the null hypothesis they had.
Answer:
5 times
Step-by-step explanation:
<span>copper +copper = copper
0.14x+0.24(100-x) = 0.20*100 = 20</span>
