Finding expected count in interval for gamma distribution with known mean and variance

[semidevil]

so I don't even know where to start and how to approach this. suppose that a set of measurements y1, y2,...y100 were taken from a gamma pdf where E(y)= 1.5, and var(y) = .75. how many y(i's) would I expect to find in the interval (1.0, 2.5).

I have absolutely no idea where to start given my information.

so I know that gamma pdf = lamda^r / (r - 1)! * ye^(-lamda*y), for y > 0.

and i know the expected value formula and variance formula, e(y) = r/lamda and variance(y) = r/lamda^2.

but so what? what do I do?

 

[TenaliRaman]

100*P(1<=y<=2.5)

-- AI