If you want to include 0, the overall interval is 115 times 0.01, or 23 times 0.05 or 11.5 times 0.10. The latter might make it harder to plot 1.14, so I'd probably use an interval of 0.05.
Between 6 or 7 and about 25 intervals on a graph's scale are about right. More makes it pretty busy and sometimes difficult to tell which mark is associated with the number. A fewer number is indicated only if there are a fewer number of discrete values that need to be shown to adequately identify the data points.
Here is all you need for b)
Answer:
2.5 hours
Step-by-step explanation:
To get the hourly speed, we need to divide 430 by 5.
This means that the train is going at a speed of 86 miles/hour.
Since we need to find the hour, we need to divide 215 miles by 86 miles/hour.
We can use the keep change flip to do 
This would give us 2.5 hours.
