Question 824031
If I'm reading it right, the road is costing the
contractor Rs 20000, and is asking
{{{ 20000 + .3*20000 = 26000 }}}
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I'm assuming that the contractor must 
stand by the quote, so only the cost changes.
Cost = {{{ 20000 + .04*20000 = 20800 }}}
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The fraction of the gain is:
{{{ ( 26000 - 20800 ) / 20800 = 5200 / 20800 }}}
The % gain is:
{{{ ( 5200 / 20800 )*100 }}}
{{{ .25*100 }}} = 25%