Answer:
The area under the speed - time graph denotes the distance travelled by the object
In the given graph, we just have to think about the first 4 seconds, we also notice that the velocity at 4 seconds is 20 m/s
The distance travelled by the object in 4 seconds is the area of the triangle in the graph with a base of 4 units and height of 20 units (image included)
Distance Travelled = Area of triangle = 1/2 * base * height
Distance Travelled = 1/2 * 4 * 20
Distance travelled = 4 * 10
Distance travelled = 40 m