Xiaoming and grandpa started from the same place in the circular field and walked back to back along the edge of the field. Four minutes later, they met. Xiaoming walks 87 meters per minute, and Grandpa walks 70 meters per minute. How many square meters is this circular venue?

The sum of the distances traveled by two people is the circumference of this circular field.

So the perimeter of this site is

(87+70)×4=628

rice

The radius of the site is

628÷3. 14÷2= 100

rice

The area is

3. 14× 100? =3 1400

square meter

A: This circular stadium covers an area of 3 1400 square meters.

Two cars, A and B, travel in opposite directions from A and B at the same time and meet at the midpoint 120km. It is known that the speed ratio of A and B is 5:7. How many kilometers is it between A and B?

At the same time, the distance traveled is directly proportional to their respective speeds. So when two cars meet, they travel the same distance.

5:7

According to the topic, the distance traveled by car A is 120km, which is less than half of the whole journey, while the distance traveled by car B is 120km, which is more than half of the whole journey. That is, when they met, car B walked more than car A.

120+ 120=240

kilometre (km)

According to the proportional relationship, the whole process is

240÷(7-5)×(7+5)= 1440

kilometre (km)

A: The distance between A and B is 1440 km.