Xiaoming and Xiaohua walk on the opposite side at the same time from two places 3000 meters apart. Xiaoming walks 80 meters per minute and Xiaohua walks 70 meters per minute. If a dog and Xiaoming walk at the same time, The time for a puppy to run is equal to the time for two people to meet, that is:

3000(80+70)= 20 minutes

The puppy ran away: 20× 400 = 8000m.

Integer multiplication algorithm for extended data;

(1) number alignment. Starting from the right, multiply the first factor by the number on each bit of the second factor, and the end of the number will be aligned with which bit of the second factor.

(2) Then add up the numbers multiplied several times.

(Multiply with 0 at the end of an integer: you can multiply the number before 0 first, then see how many zeros are at the end of each factor, and add a few zeros at the end of the multiplied number. )