200 ${м}^2$ = (200 : 100) а = 2 а;
3000 ${м}^2$ = (3000 : 100) а = 30 а;
6500 ${м}^2$ = (6500 : 100) а = 65 а.
 
450 ${м}^2$ = (400 : 100) а + 50 ${м}^2$ = 4 а 50 ${м}^2$;
765 ${м}^2$ = (700 : 100) а + 65 ${м}^2$ = 7 а 65 ${м}^2$;
8435 ${м}^2$ = (8400 : 100) а + 35 ${м}^2$ = 84 а 35 ${м}^2$.