2. Yes; Yes (); () Yes.

3, according to the formula to supplement the conditions or questions.

(1) There are two ropes, one is 23 meters long, how long is the second one?

①23 × 13 ; ②23 + 13

③23 ×( 1- 13 ) ; ④23 ×( 1+ 13 )

(2) A book has 100 pages. How many pages have you read?

100× 15 ; 100×( 1- 15 )

(3) A 400-meter road has been built 15.

400× 15 ; 400×( 1- 15 )

(4) bright primary school planned to plant 1200 trees. As a result, 58 trees were planted for the first time and 35 trees were planted for the second time.

① 1200×35

② 1200×(58 -35 )

③ 1200×(58 +35 - 1)

4, () is 45 of 40; 40 is 45 of ()

More than 20 kg 14 is () kg; 20kg is smaller than () 15

5. A pile of coal weighs 45 tons, and it takes 10 hour for a truck to transport it. Then, it will take 4 hours to finish the work.

Service () (), 35 hours to complete the task.

6. From place A to place B, car A needs 10 hour and car B needs 15 hour ... The speed ratio between car A and car B is (). At this speed, the time ratio between a car and b car from b to c is ().

7. A rope is 5 meters long and divided into 8 segments on average, each segment is meters long and each segment accounts for the whole length.

8. Enlarge the former item of a ratio by 2 times and reduce the latter item by 2 times, and the ratio is ().

9. A rice mill can grind rice tons per hour, 1 hour can grind rice () tons, and it takes () hours to grind rice 1 ton.

10, and the ratio of side lengths of two cubes is 3: 2; The ratio of the surface areas of large and small cubes is (); The volume ratio of large and small cubes is ().

1 1, 1 ton rapeseed can squeeze tons of oil, 140 ton soybean can squeeze tons of oil; It takes () tons of soybeans to squeeze 140 tons of oil.

12. A bucket of water can fill 10 bowls or 12 cups. Pour 5 cups of water and 3 bowls of water into the empty bucket, and the water level accounts for () () of the bucket height.

13、( )20 =20÷( )=8:( )=0.8=( )%

14 and 120 increase 15%, which is (). () 10% is less than 60.

15, 45 meters is 90 meters ()% 5 tons is 500 kilograms ()%,

() is 80% of 20m () is more than 8, 10%, and 4 hours is less than 20% of ().

16, the oil yield of one rapeseed is 35%, 400 kg rapeseed can extract () kg oil, and it takes () kg rapeseed to extract 1400 kg oil.

17, (): 20= 12() =24÷( )=( )%= 20% = () fold.

18. Add () kg of water to 30 kg of salt, and you can get brine with a salt content of 30%.

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