1. Three-fourths divided by three-sevenths means (4/3/7/3), the quotient is (4/7), and a number divided by a fraction equals a multiple of the number (divided by the reciprocal of this fraction).

2. In 9/ 10: 3/5, the previous term of the ratio is (10/9) and the ratio is (2/3). If the nine-tenths are tripled, three-fifths should keep the proportion unchanged.

The reciprocal of two sevenths is (2/7), and the number whose reciprocal is 0.4 is (4/5).

A piece of wood is 5 meters long. Divide it into four parts on average, each part is (4/ 1) meters, three quarters of it is used, and the rest is (3/20) meters.

In the same circle, the ratio of radius to diameter is (2: 1).

6. Arrange the following figures in descending order.

57.2% 0.5777777 ... four fifths 0.6666 ...

(0.6666 ...< 57.2% < 0.57777 ...