Current location - Training Enrollment Network - Mathematics courses - Winter vacation homework's answer in the seventh grade of mathematics.
Winter vacation homework's answer in the seventh grade of mathematics.
Solution:

Because point C is the point where we first met.

So during the whole journey, A can run 30 kilometers.

Because point D is the point of the second meeting, it took 2×2- 1=3 times for the second meeting.

30× 3 = 90 straight line

Suppose the whole journey is x kilometers.

Then BD=x-AD=x-40.

90=x+x-40

130=2x

x=65

BD=65-40=25

BC = 25+CD = 25+(40-30)= 35(B's way)

So speed A: speed B =30:35=6:7.

Let the speed of vehicle A and vehicle B be V 1, and the distance between V2 and AB be x kilometers, from the meaning of the question:

30/v 1=(x-30)/v2,( 1)(30+40)/v2 =(x-30+x-40)/v 1,(2)

(1) is reduced to 30/(x-30)=v 1/v2.

(2) Simplified to 70/(2x-70)=v2/v 1,

The phase of the two formulas * cancels V 1, and V2 is: 2100/[(x-30 (* (2x-70)] =1.

2 100=(x-30)*(2x-70)=2x^2- 130x+2 100

x=65

v 1/v2 = 30/(65-30)= 30/35 = 6/7

That is, AB is 65 kilometers apart, and the speed ratio of A to B is 6:7.

I am a teacher. Thank you for your adoption.