(1*3*5+2*6*10+3*9*15+4*12*20)/(1*2*3+2*4*6+3*6*9+4*8*12)
=1*3*5(1+2^3+3^3+4^3)/1*2*3(1+2^3+3^3+4^3)
=1*3*5/1*2*3
=5/2