The ratio of third proportional to 12 and 30 and the mean proportional between 9 and 25 is:

12, 30 का तीसरा समानुपाती = $(30^2)/12 = 900/12 = 75$। 9, 25 का मध्यानुपाती = $sqrt{9*25} = 3*5 = 15$। अनुपात = 75:15 = 5:1।