1. 1/4*3 1/6+( 1+25%)*45/6

=3 1/24+5/4×45/6

=3 1/24+225/24

=256/24

32/3

2.(3-45% divided by 90%) divided by 6/ 15

=(3- 1/2)÷2/5

=2.5÷0.4

=6.25

3、( 12.5%* 1/9)*40%* 18

= 12.5%×40%×2×9× 1/9

= 1/ 10× 1

= 1/ 10

4、23/5-8/ 13*260%

=23/5-8/5

= 15/5

=3

Second, the application problem (2)

1, Xiaohua goes to complete a task. On the first day, she finished all 1/4, and on the second day, she finished all 3/5. Find the ratio between the tasks completed two days ago and the remaining tasks, and find the ratio.

1/4+3/5= 17/20 1- 17/20=3/20

17/20:3/20= 17:3

2. There are 1680kg in two piles of coal, 7.5% in the first pile of coal and 2/3 in the second pile of coal, and the remaining amount of the two piles of coal is equal. How many kilograms were there in the original two piles of coal?

1-7.5%)÷( 1-2/3)+ 1=3775/ 1000

1680 ÷ 3775/1000 ≈ 445 (ton)

1680-445= 1235 (ton)