Physics paper 1 problem, help plz

[abdelm]

I was solving paper 1 June and november 09 and there was similar questions about speed time graph. For example, in the nov 09 it gives u a graph and asks how much did the guy travel before reaching constant speed and he gives u the speed 20M/s and time 10s so, I do it with the rule speed equal distance over time to get the distance, i get it 200m but the marking scheme says it's 100.

Same In June, he asks how much the guy traveled with 10m/s and in time 5s, so I get it 50 but the marking scheme says it's 25.what am I doing wrong here?

 

[AG316]

it is because a triangle and you half your answer
the formula of a triangle is =bh1/2

 

[abdelm]

Oh I get it now, thanked a lot!