how many pounds of gravel that cost $2.50 per pound must be mixed with 6 pounds of cement that cost $1.50 per pound to make a mixture that cost $2.50 per pound?

Assume that adults have iq scores that are normally distributed with a mean of mu equals 100 and a standard deviation sigma equals 20. find the probability that a randomly selected adult has an iq between 80 and 120.assume that adults have iq scores that are normally distributed with a mean of mu equals 100 and a standard deviation sigma equals 20. find the probability that a randomly selected adult has an iq between 80 and 120.