Decimals between 15 & 16, with an interval of 0.2 between each pair of decimals

There are a couple of ways we could answer this.  The obvious one is

15.2, 15.4, 15.6, 15.8

They're between 15 and 16, .2 between consecutive elements

So is

15.1, 15.3, 15.5, 15.7, 15.9

So is

15.107, 15.307, 15.507, 15.707, 15.907

- "runner b is moving at a slower rate."

- "the graphs shown are graphs of distance(km) against time(min).

the slopes of this graphs are are given by:

slope = (change in y)/(change in x)

= (change in distance)/(change in time)

this is the formula for finding the speed. so, the slope of these graphs represent the speed of the runner.

taking each division in the graph to represent 1 on both axis:

runner a ⇒ speed = (2-0)/(1-0)

= 2/1

= 2 km/min

runner b ⇒ speed = (3-0)/(3-0)

= 3/3

= 1 km/min

this shows that   runner b is moving at a slower rate."