There is a circular swimming pool in the park. Grandpa runs around the swimming pool 20 times a day. If the radius of the swimming pool is 38 meters, how many meters does Grandpa Li Run swim every morning?

Solution: Run 2× 3.14× 38× 20 = 4772.8m every day.

7. The newly developed roller has solved a difficult problem of expressway in China. Front wheel radius 1.5m, 8 revolutions per minute. How many meters does the roller advance per minute?

Solution: Forward 2× 3.14×1.5× 8 = 75.36 m.

There are 360 red balloons and yellow balloons in the shop, of which 25% are red balloons and 24 are yellow balloons. The remaining red balloons and yellow balloons are just equal. How many are Red Balloon and Yellow Balloon?

Solution: 24 yellow balloons were sold, leaving 360-24=336.

At this time, the yellow balloon is regarded as the unit of 1, so Red Balloon has 1/( 1-25%)=4/3.

Originally there were 24+336/(1+4/3) = 24+144 =168 balloons.

Originally there were 360- 168= 192 Le Ballon Rouge.

9. Two-fifths of the freight in a warehouse was originally shipped out, and then 8400 tons were brought in, 30% higher than the original. How many tons of original goods are there in the warehouse?

Originally regarded as 1 unit.

After 2/5 shipment, there is still 1-2/5=3/5.

So it is 8400/(1+30%-3/5) = 8400/0.7 =12000 tons.