Ascale drawing is 21 inches long and 9 inches tall the real item is 30 feet tall how long is it

So this is a proportion.  The scale is 9 inches tall and the real is 30 feet.  First, multiply feet by twelve to find inches.
So the real item is 360 inches tall.  So the proportion is 9:360.  Or 1:40.  The scale is 1/40 the size of the real item.  Or the real item is 40 times the size of the scale.
So if the scale drawing is 21 inches long, that means the real item is 40 times longer, or 40·21
Therefore the real item is 840 inches long.  Divide it by twelve to find how many feet long it is.
840/12=70
Therefore the real item is 70 feet long.
70ft

This is easy:) first lets set them up within fractions.
  
   9 tall             30 tall
 ->  
  21 long          x long
since we don't know how long the second one is we just put x for now ;)

now in order to find the scale factor we need to divide 30 by 9 so lets do that 
30 ÷ 9 = 3.33333333333333333333333
a good estimation* 
so that means in order to get 30 we multiplied 3.3333333333333333333 and  9 
now in order to figure out x finally we can do the same 
so take 21 and multiply by 3.33333333333333333333333333
21 x 3.3333333333333333333333333333 = 69.99999999999999999999
and 69.9999999999999 is rounded out to be 70
so our answer here is 70
also in answer form:
the real item is 30 feet tall and 70 feet long:)
i hope this was helpful:)
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