[tex]Look\ at\ the\ picture.\\\\2\ sides:\ 15cm\times15cm\\\\Area:A_1=2\times(15cm\times15cm)=2\times225cm^2=450cm^2\\\\4\ sides:15cm\times20cm\\\\Area:A_2=4\times(15cm\times20cm)=4\times300cm^2=1200cm^2\\\\Area\ of\ the\ block:\\\\A=A_1+A_2\\\\\boxed{A=450cm^2+1200cm^2=1650cm^2}[/tex]
