Current location - Training Enrollment Network - Mathematics courses - How to do the fifth question on page 10 of the math exercise book for primary schools in Beijing Normal University?
How to do the fifth question on page 10 of the math exercise book for primary schools in Beijing Normal University?
One, two people should go this way. A It takes 30 minutes to walk and 20 minutes to walk. After walking for 3 minutes, A found that she didn't take anything, which delayed for 3 minutes. I walked for a few minutes before I saw him.

Solution: A is 3+3+3=9 minutes later than B.

Think of the whole distance as 1.

Then the speed of a = 1/30.

Speed B = 1/20

When Party A packed up and set out, Party B had already left 1/20×9=9/20.

Then the distance between Party A and Party B is1-9/20 =11/20.

The sum of the speeds of Party A and Party B =1/20+1/30 =112.

Then meet again in (11/20)/(112) = 6.6 minutes.

for reference only