Answer:
1/2 or 50% of the population has heard the rumor when it is spreading fastest.
Step-by-step explanation:
We need to take the derivative with respect to y from the r(y) = dy/dt = 2y(1-y) and equal to zero. At this condition we maximize the function and will get the maximum of the rumor spreading.
[tex]\frac{d(r(y))}{dy}=2-4y=0[/tex]
Therefore we just need to find y:
[tex]y=2/4=1/2[/tex]
So 1/2 or 50% of the population has heard the rumor when it is spreading fastest.
I hope it helps you!