80% - 

$$ {4} \over {5} $$

70% - 

$$ {7} \over {10} $$

25% - 

$$ {1} \over {4} $$

0.19 - 

19%

0.09 - 

9%

0.9 - 

90%

0.3 - 

30%

50% of a number - 

Halve the number

10% of a number - 

Divide the number by 10

1% of a number - 

Divide the number by 100

100% of 170 km - 

170 km

50% of 170 km - 

85 km

10% of 170 km - 

17 km

1% of 170 km - 

1.7 km

100% - 

112

10% - 

11.2

1% - 

1.12