Question 1127937
the scale is 1 inch = 2.5 ft
You need to scale down the silo to the
smaller scale. 
2.5 ft converts to 1 inch
1 foot  converts to 1/2.5 inches
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15 ft wide
{{{ 15*( 1/2.5 ) = 6 }}} inches
75 ft long
{{{ 75*( 1/2.5 ) = 30 }}} inches
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If you need to convert back, use
the original 1 inch converts to 2.5 ft
{{{ 6*2.5 = 15 }}}
{{{ 30*2.5 = 75 }}}
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hope this helps