2.2 points 1. The product of this number multiplied by its reciprocal is 1, and this number is 3- 1=2.

3.2 points 1. 1:2。 Both numerator and denominator are multiplied by 4;

4.6。 7。 9。 Let the proportions of Party A, Party B and Party C be 6x, 7x and 9x respectively, then the sum of the three numbers =(6+7+9)x= the average of the three numbers *3, and 22x=22, that is, x= 1, so, ...

5.350 copies. If this batch of books is ***y, some books are distributed to students in grades 5 and 6 (4/5) * y, and grade 5 will get (4/5) * y * (3/7) = 120, which is simplified (12) * y =

6.27.5 kg. Let * * have x kilograms of oil, and then take (1-41) x * (2/5) = (1) * x+7.5 for the second time, and get the solution of (1/20) x = 7.5.

7.20 kilograms. Let this barrel of oil weigh x kilograms, then (1-3/8) * x = (5/8) * x =12.5, and x=20.