Question

Dau coroana.
Aflati aria totala a unui cub cu muchia de:
8cm
5 intreg si 1pe 6cm
2,1(3)cm.

Answer 1

1) l cub = 8 cm
   At cub = 6l² = 6 · 8² = 6 · 64 = 384 cm²

2) l cub = 5 intregi si 1/ 6 cm = ( 5 · 6 + 1) / 6 = 31 / 6 cm
   At cub = 6l² = 6 · ( 31/ 6)² = ( 6 · 31²) / 6· 6 = 31² / 6 = 961 / 6 cm²

3) l cub = 2,1( 3) cm
   l cub = ( 213 - 21) / 90 = 192 / 90 = 96 / 45 = 32/ 15
   l cub = 32/ 15 cm
  At cub = 6l² = 6 · ( 32 / 15) ² = 6 · 32²/ 15² = 6 · 1024 / 225 = 2 · 1024 / 75
  At cub = 2048 / 75 cm²