My Math Forum Width of the river

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October 18th, 2018, 11:12 AM   #1
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Width of the river

You want to swim across the river. Before you get in the water you want to work out approximately how far it is to the other side.

Use the map below to estimate the width of the river.

The river is approximately

metres wide
This answer will be marked within a reasonable range.
Attached Images
 rivercrossing.jpg (14.9 KB, 9 views)

 October 18th, 2018, 11:50 AM #2 Senior Member   Joined: Feb 2016 From: Australia Posts: 1,770 Thanks: 627 Math Focus: Yet to find out. ? A scale is given in the diagram. What are you struggling with exactly?
 October 18th, 2018, 12:05 PM #3 Member   Joined: Aug 2018 From: Warrington Posts: 50 Thanks: 1 how to work out the scale
 October 18th, 2018, 01:05 PM #4 Math Team   Joined: Jul 2011 From: Texas Posts: 2,847 Thanks: 1486 so ... what would you estimate the width to be? Thanks from Denis and Joppy
 October 18th, 2018, 10:00 PM #5 Member   Joined: Aug 2018 From: Warrington Posts: 50 Thanks: 1 20m i would say
 October 18th, 2018, 11:07 PM #6 Senior Member   Joined: Apr 2014 From: UK Posts: 898 Thanks: 329 Are you estimating the width where the dotted line is, which is also where skeeter has pasted a rotated scale in his post?
 October 18th, 2018, 11:58 PM #7 Global Moderator   Joined: Dec 2006 Posts: 20,383 Thanks: 2011 The dashed line seems to correspond to about 29 m.
 October 21st, 2018, 05:47 PM #8 Senior Member   Joined: May 2016 From: USA Posts: 1,310 Thanks: 550 Set a compass so that the legs are set to equal 20 on the scale. Now place one leg at one end of the dotted line. Without moving the first leg, place the other leg on the dotted line. Does the compass reach all the way across? Not at all. So the width is more than 20. Now swing the compass keeping the leg on the dotted line still. Now does the other leg reach the other side. Yes, and far beyond it. So the width is less than 30. Reset the compass on the scale for 10. You will find that three measurements are pretty close, but a little bit more. So almost 30, but not quite. 29 is a reasonable approcximation.
October 21st, 2018, 05:49 PM   #9
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Quote:
 Originally Posted by JeffM1 Now place one leg at one end of the dotted line. Without moving the first leg, place the other leg on the dotted line.
You do the hokey pokey and that's what it's all about.

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