probability and integrals

Question

Suppose that f(x) is the probability density function describing the distribution for the number of minutes it takes to solve a puzzle. Which of the following represents the probability that you will solve the puzzle in 8-10 minutes?

a. f(10)-f(8)
b. (10 on top, 8 on bottom)∫f '(x)dx
c. (∞ on top, 0 on bottom)∫[f(10)-f(8)]dx
d. (10 on top, 8 on bottom)∫f (x)dx
e. none of these

Answer 1

the probability that you solve it between 8 and 10 minutes is the integral from 8 to 10 ----∫ƒ(x)dx. This is answer d)