①

5

6

×

5

6

=

25

36

；          ②

3

7

×

7

3

=1；           ③

2

5

×5=2；          ④

5

7

×

3

14

=

15

98

；

⑤

5

8

×

24

5

=3；               ⑥4²×π≈50.24；       ⑦2²×π=12.56；       ⑧3²π=28.26．