2 out of 7 times () = 3 out of 13 times () = 9 out of 17 + () = 9 out of 7 - () = 1

RELATED INFORMATIONS

• 1. A bag contains seven balls of the same size, including three red balls, two black balls and two white balls, Take 2 balls continuously from them (do not put them back after taking them) (1) The probability of getting the red ball for the second time
• 2. 58 / 78 reduction ratio
• 3. If ∠ 1 = 38 ° 5 ′ 46 ″, ∠ 2 = 72 ° 18 ′ 8 ″, then 3 ∠ 1 - half ∠ 2 =?
• 4. Simple operation of 888 times 9 and 111 times 28
• 5. Simple calculation of 222 × 85 + 111 × 30
• 6. Mathematics multiplication and division formula For example, if one factor remains unchanged and the other factor is multiplied by several, the product obtained is equal to the original product multiplied by several.
• 7. When calculating the division, Xiao Chun wrote the divisor 72 as 27, and the result showed that the quotient was 26 and the remaining 18. What is the correct quotient?
• 8. Please use the formula to solve the problem A research team observed and recorded the growth of three bacteria (labeled as 1, 2 and 3 respectively for the convenience of research) attached to the surface of the object. The three bacteria split into two in the first hour and produced new bacteria (labeled as 4, 5, 6, 7, 8 and 9 respectively), and then changed according to this rule every day, that is, each bacteria split into two, The formation of new bacteria (members of the research group use the figure as shown in the figure to record the image). Then how many hours will the bacteria labeled 120 appear?
• 9. When calculating division, he mistakenly took the divisor 43 as 34, and the remainder of 32 is 32. What is the correct quotient and remainder?
• 10. In the calculation of a problem, the divisor 65 is regarded as 56. The result shows that the quotient is 13 and the remainder is 52. What is the correct quotient?
• 11. The simple calculation is 37.58 × 97
• 12. Simple calculation: 1, 8.32 * 34 + 8.32 * 66 2, 37.5/25 + 62.5/25 3, 7.25-0.68-6.25
• 13. 1 / 2 + 1 / 4 + 1 / 8 + 1 / 16 + 1 / 32 + 1 / 64 simple operation, write out the specific process
• 14. Simple operation of 99 times 26
• 15. Simple calculation of 72 × 0.99
• 16. How to calculate 3.8 * 2 + 3.8 * 99
• 17. 24（）1.5＝25.5.24（）0.3＝23.7.24（）0.3＝24.3.24（）1.5＝36.24（）1.5＝22.5.24（）0.8＝30. 24 () 0.8 = 23.2 (fill in operation symbol)
• 18. 18: 32 0.25:1.8 12:11:9 22 1.2:4 3 18:32 0.25:1.8 11 out of 12: 22 out of 9 1.2:3 / 4
• 19. Find the nth number 1,4,9,16,25,36
• 20. 1,4,9,16,（）,（）,36,49... 1,1,2,3,5,8( ),21,34...