In a class of 80 students,40 study physics,48study mathematics and 44 study chemistry,20 study physics and mathematics,24 study physics and chemistry and 32 study only two of the three subjects. Of every student studies at least one of the three subjects. Find ; 1.The number of students who study all the three subjects.2.The number of students who study only mathematics and chemistry.

Answer is in the photo. I couldn't attach it here, but uploaded it to a file hosting. link below! Good Luck!

cutt.ly/kzH1l58

- "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."