I need help with a question we had in my exam. I got the paper online afterwards, but I still don't understand it, and want to understand how to solve it. I haven't done this topic.
http://i.prntscr.com/b94f16a0b1e5426dad26397d8cb430a8.png [Graph with the Answer, which is 7b(ii)]
http://i.prntscr.com/ea86d6627ba34438b9c916b791d1cbc0.png [The Question]
You can approximate the tangent at $h=0.1m$ as the line between the two point adjacent to $(0.1,0.7)$. Each of the small squares along the horizontal represent 0.005m. Each square along the vertical direction is 0.02 m/s. The coordinates of those points are (0.12,0.76) and (0.09,0.66). The slope is therefore something like (0.76-0.66)/(0.12-0.09)=0.1/0.03=3.4