Two numbers are in ratio 4:5 and their LCM is 180. The smaller number is

Explanation:-

Let two numbers be 4x and 5x;
their LCM = 180 and HCF = x; Now,
1^st number * 2^nd number = LCM*HCF
Or, 4x*5x = 180*x;
Or, 20x = 180;
Or, x = 9;
then, the smaller number = 4*9 = 36.