Projectile motion question?

If I have the right diagram, then, we see that it is a distance / time graph. The first thing you need to do is draw in the points with a smooth curve. When I was at school I used to have something called a 'French curve', which sounds a bit but what it is is a flexible bar of lof lead covered with a thin coat of rubber and you could bend it into any curved shape you like. You would line it up along the dots and draw a smooth curve. Anyway, back to your question. Recall that the slope of the tangent line to a distance / time graph is, by definition, the velocity. So you draw a tangent line to the curve at the point where the time is 1.2 seconds. Then you can work out the change is distance over the corresponding change in time to give you the speed at that time.