For a fraction, the numerator minus 1 equals 1 / 3; the denominator minus 1 equals 1 / 2. What's the number? Primary school mathematics book 10 thinking questions

Let the numerator be x, the denominator be (x-1) * 3 = 3x-3, 2x = 3x-3-1, x = 4, and the number is 4 / 9

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1. There's a fraction where the addition of 2 to the molecule equals 3 / 5, and the subtraction of 2 from the molecule equals 1 / 3
2. 5:8 to 1:4 (ratio) 0.6 to 1:2 (ratio) 0.5T to 200g (reduction ratio) 5:16 to 0.25 (reduction ratio) 0.36 to 6 0.8 * 2 / 3 + 1 / 5 / 0.75
3. 54 out of 35 to 3.5
4. Observe the following formulas: 21-12 = 9; 75-57 = 18; 96-69 = 27; 84-48 = 36; 45-54 = - 9; 27-72 = - 45; 19-91 = - 72 (1) Please complete the above rule with words: exchange the ten and one digits of a two digit number. What is the difference between the new two digits and the original two digits______ (2) can you explain this rule with what you have learned? Give it a try
5. There are 440 boys in Hongxing primary school. The number of boys is 22 / 15 of the number of girls. What is the number of the whole school? Use equation to calculate equation
6. The number of female students is two fifths less than that of male students. What number is two fifths equal to
7. Two fifths of a number is 60. What's 20% of the number,
8. Given that two fifths of a number is three fourths, how much is the number? The formula is ()
9. Three quarters of a number is 35 more than two fifths of it. Find the number
10. 1. Arrange 3 / 10, 2 / 7, 5 / 8 from large to small. 2, 4 and 2 / 5, 4 and 5 / 8, 4.5 from large to small
11. 7 / 5 of a number is 27 more than 3 / 8 of it. What's the number
12. The number 32 less than four fifths of a number is 28. Find this number
13. Find the rules and fill in the blanks (4 / 3, 1 / 9, 8 / 5)
14. Fill in the blanks according to the rule: 160%, 120%, two fifths, 0
15. What is the ratio of 0.125:5 in 8? What is the ratio of 7 in 12:3 in 8
16. Two fifths × two thirds + two fifths ／ two thirds = [] [process, simple calculation]
17. Simple calculation: 24 / 5 × 11 / 8 + 61 / 10 △ 8 / 5 + 13 / 10 × 11 / 8
18. Two thirds X: two fifths = fifteen sixteenth: eight ninths
19. Thirteen by two fifths by one thirteenth by five seventeen It's necessary to make the calculation simple and urgent!
20. The ratio is 1 / 4 to 1 / 9, 0.5 to 0.015, 7 / 5 to 5 / 2, 2 / 5 tons to 800 kg, and 1 / 4 to 20 Three quarters of a meter is more than 750 meters