Nov 2004, paper2 , answer 6
a) speed = distance / time
distance = 120-72 = 48.
time = 0830 - 0800 = 30 minutes = 0.5 hour
therefore speed = 48/0.5 = 96km/h
b) At 0900 hours, the distance covered is 0 because it is not moving (the line is constant at 40). Time = 1 hour. 0/1 = 0
By the way speaking of calculators and this question...
My teacher told me a really cool trick in the calculator... If u have the (.,,,) button, you can use it to answer the questions that tell you to for example calculate the time of arrival. All you gotta do is put the hours(here 0830) like this: 08(press the button)30(press it)00(press), then - 08(press)00(press)00(press). It will give u the answer and u can change from decimels to hours and minutes by pressing the button (like the S<>D). By the way the first press is for hours, then min, then sec.
Hope u understood this cuz its really helpful