Find the mistake and correct it

III  Find the mistake and correct it.

     1.  When we are on holiday, we used to go to the beach every day.          

     2.  None of them had any idea about how make a raft with only a few              ................

          bamboo canes.

     3.  He said that they will have to set off soon after midnight.              

     4.  When he lived in Japan, he didn’t used to eat food with forks,         

          but with chopsticks.

     5.  He thinks that geometry is not as difficult than arithmetic.