sentence1: There are 8 balls . 7 of them weigh the same . 1 of them has a different weight , -LRB- you do n't know if it 's heavier or lighter -RRB- . How do you find the odd ball with 2 weighs ?
sentence2: How many 4 digit numbers can be formed by using 0 , 1 , 2 , 3 , 4 , 5 , 6 , and 7 ? How many of them are between 4000 and 6000 ?