So half life is the time taken for a sample to decay to half its original mass, its a constant and applies to any original mass, it could be 5g or 1kg, it will take the same amount of time for the original mass to half. In this case the half life is 3 days.
After 3 days the sample will be at half its original mass, now 50g.
Now we can treat the 50g as if its a new sample. After another 3 days (6 days in total) there will be half of 50g left, = 25g.
Answer:
I think the answer is the 3rd one
The hills and valleys decrease the height and speed of the ride. This means that the graph has a negative correlation.
By the way, I think you may have plotted your points incorrectly. The directions said to connect them all with a smooth line or curve.
Also, this is not high school chemistry. This is more likely to be elementary school science. Just make sure that you put your questions in the correct categories next time! :)