Daca 6 muncitori au sapat in 10 zile 420 m de sant.
=> 6 muncitori au sapat in 1 zi 420 / 10 = 42 m de sant
=> 1 muncitor a sapat in 1 zi 42 / 6 = 7 m de sant
=> 10 muncitori in 1 zi vor sapa 10 * 7 = 70 m sant
=> 10 muncitori in 8 zile vor sapa 70 * 8 = 560 m sant