smc

Question

The formula N=8 10^8 x^-3/2 gives, for a certain group, the number of individuals whose income exceeds x dollars. The lowest income, in dollars, of the wealthiest 800 individuals is at least:

Accepted Answer

Plug 800 for N because 800 is the number of people who has at least x dollars. 800 = 8 10^8 x^-3/2 10^-6 = x^-3/2 In order to undo raising to the -32 power, raise both sides to the -23 power. (10^-6)^-2/3 = (x^-3/2)^-2/3 x = 10^4 dollars The answer is 10^4.