Solution: 1 This number is the power of 2-1, the second number is the square of 2-1, and the third number is the cube of 2-1.

3. Party A and Party B drive in the same direction from the same place, with Party A walking m kilometers per hour and Party B walking n kilometers per hour. (m > n) Party B is one hour ahead of Party A, and Party A can catch up with Party B after (na/(m-n)) hours.

Solution: Time taken to catch up = distance divided by speed difference, and the distance that B goes first is the distance that A needs to catch up.

4. A ship sails downstream at a speed of 20 kilometers per hour and upstream at a speed of 65,438+05 kilometers per hour. It takes 2 1 hour for this ship to make a round trip between Port A and Port B in this channel. The distance between Port A and Port B is (180) km.

Solution: Let the distance from port A to port B be x kilometers, and x/20+x/ 15=2 1. According to the time spent downstream+the time spent upstream =2 1, the equation holds.

5. Calculate11+13+15+...+37 = (11+37) *14/2 = 336.

Solution: This is arithmetic progression and Gauss algorithm. Method: (beginning+end) * * * Several numbers /2.