Question 720122
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how to solve this question ?
1) a road is 2 km long. what is the length of the road on a map of scale 1:20000 ?
2) a map uses a scale of 1:5000. what is the actual length of a river if it measures 5cm on the map? 
give your answer in km. 
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<pre>
(1)  A road is 2 kilometers long. 2 kilometers is 2000 meters.

     The scale 1 : 20000  means that 1 centimeter on the map is 20000 centimeters in the field.

     It is the same as to say that 1 centimeter on the map is 200 meters in the field.

     2000 meters is 10 times 200 meters.

     Hence, according to common sense (or the law of proportion), 10 centimeters on the map is 2000 meters in the field.

     Thus the length of the road on the map is 10 centimeters.    <<<---===  <U>ANSWER</U>.




(2)  A map uses a scale of 1:5000.  It means that 1 cm on the map corresponds to 5000 cm in the field,

     i.e. 1 cm on the map corresponds to 50 meters in the field.

     Hence, according to common sense (or the law of proportion), 

     5 centimeters on the map corresponds to 5*50 = 250 meters in the field.    <<<---===  <U>ANSWER</U>
</pre>


That's all.  &nbsp;&nbsp;It sounds as a song or as a poem.  &nbsp;&nbsp;Because the common sense follows to law of harmony.



Now compare it with the composition by &nbsp;@Theo in his post.


It is a collapse of a brain. &nbsp;Why inches ? &nbsp;Why these unnecessary conversions ? &nbsp;Nobody asked about inches . . . 

Nobody asked about these decimal fractions . . . It is a collapse . . . 


I advise you to ignore the post by @Theo - escape and run from it - - - as fast and as far as you can.


I completed.


My reader, &nbsp;I wish you to live in harmony forever, &nbsp;with a well-functioning brain. 


In such simple problems/assignments, &nbsp;you better lean on your common sense rather than crazy compositions.



&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;When you learn &nbsp;Math &nbsp;(or &nbsp;Science, &nbsp;or everything), 

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;it is of critically importance to learn from good sources.