Ans: Option (D) 25%
Step-by-step explanation:
In this case you need to find the area under the curve, which would essentially be the probability of a value in the sample space.
Now the range given is from 60 to 80; it contains the mini-triangle.
The area of the triangle = (1/2)*base*height
Since base = 80 - 60 = 20
Height = 0.025 - 0 = 0.025 (see in the graph)
Therefore
The area of the triangle = 1/4 = 0.25 which is essentially be the probability.
In percentage form, it is 25% (Option D)