Find the mean proportion of : (i) 5 and 80 (ii) and (iii) 8.1 and 2.5 (iv) (a - b) and (a 3 - a 2 b), a b.

(i) Let the mean proportion be x. Hence, the mean proportion is 20. (ii) Let the mean proportion be x. Hence, the mean proportion is . (iii) Let the mean proportion be x. Hence, the mean proportion is 4.5. (iv) Let the mean proportion be x. Hence, the mean proportion is a(a - b).