আমরা জানি

       ল.সা.গু     = দুটি সংখ্যার গুণফল × গ.সা.গু

                        = ৫ × ৬ × ৪ 

নির্ণয় ল.সা.গু  = ১২০। 

suppos two numbers are 5x and 6x  and also given that the GCD(Greatest common devisor) of two numbers is 4.

we know that the relation between GCD and LCM(Least common devisor) is LCM=(X1*X2*X3……Others numbers)/GCD.

 Now, GCD of 5x and 6x  GCD=(5x*6x)/30x        [ 30x is LCM of 5x and 6x and it found out by common formula of LCM ]

                                        GCD=x  and we define that it is equivalent of  4. so we can write GCD=x=4.

          therefor the  numbers are 5*x=5*4=20 and 6x=6*4=24  and GCD=4

      Finally LCM=(24*20)/GCD(24,20) = (24*20)/4=120 (Ans)