Here is a velocity-time graph:
The area under the line in a velocity-time graph represents the distance travelled. To find the distance travelled in the graph above, you need to find the area of the light-blue triangle and the dark-blue rectangle.
The width of the triangle is 4 seconds and the height is 8 metres per second. To find the area, you use the equation:
area of triangle = ½ × base × height
So, the area of the light-blue triangle is ½ × 8 × 4 = 16 m
The width of the rectangle is 6 seconds and the height is 8 metres per second. So, the area is 8 × 6 = 48 m
The area of the light-blue triangle plus the area of the dark-blue rectangle is:
16 + 48 = 64 m
This is the total area under the distance-time graph. This area is the distance covered.