1, 27.5cm

2、( 16)、( 1)、(25)、(2.5)

4、( 108)、( 12:23)

5. Red

6、(8, 10)

7、(3608025)、(360.8025)

8、2400

9、20

10、4: 1

Simple calculation

I. 4/15× 0.35+0.65 ÷15/4

=4/ 15×0.35+0.65×4/ 15

=(0.35+0.65)×4/ 15

=4/ 15

Second, 10.69-2.5×2.4

= 10.69-2.5×4×0.6

= 10.69- 10×0.6

= 10.69-6

=4.69

application problem

First, the water consumption last month was 160+40=200, so the saving percentage was 40/200=20%.

Second, the first one is to find the lateral area of the cylinder (2πr×h=7.2π) plus the bottom area (πr2=9π), which is 16.2π in total. The storage capacity is the volume of a cylinder, and the bottom area is multiplied by the height (10.8π).

3. The speed of the express train is 45×6÷3=90 (km/h), and the distance between Station A and bilibili is 90× (6+3) = 8 100 km.

Fourthly, the ratio of the number of pages read on the first day to the remaining pages is 1: 5, which means that one-sixth of the pages were read on the first day, and the number of pages read on the third day was 1- 1/6-2/7=23/42. The total number of pages read is 23/(23/42)= 1