Question 1097515
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Let "M" be the the total amount/(mass) of the original mixture,

and let "x" be the fraction  of corn in the original mixture (the unknown under the question).


Then the amount of corn after replacing is  (0.75*xM + 0.25*M),
and the equation for the given corn percentage is


{{{(0.75*xM + 0.25*M)/M}}} = 0.55.


Cancel the factor M in the numerator and denominator. You will get


0.75x + 0.25 = 0.55  ====>  0.75x = 0.55 - 0.25 = 0.3  ====>  x = {{{0.3/0.75}}} = {{{2/5}}} = 0.4.


<U>Answer</U>.  The percentage of corn in the original mixture was 40%.
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