1, 4.5 to 10/7, the simplest score ratio is 63/20, and the ratio is 3. 15.

2.a and three sevenths are reciprocal. The decimal unit of A is 1/3, and it has seven such decimal units.

3.5 hours and 45 minutes = 5.75 hours

4, a rope cut off a quarter of the total length, just cut off two-thirds of the meter. This rope was originally 8/3 meters long, and there are 2 meters left.