Three digit numbers xyz are formed with digits 0, 1, 2, ….., 9 such that x≤y≤z  then number of such numbers is

x < y < z ⇒  number of numbers = C9,3 x = y < z ⇒number of numbers = C9,2x < y = z ⇒number of numbers = C9,2x = y = z ⇒number of numbers = C9,1 Total numbers =  9C3+ 9C2+ 9C2+9=165