A man bought some apples at a certain price. Find price per 100 apples

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A man was asked what price per 100 he paid for some apples, and his re-
ply was as follows: “If they had been 4¢ more per 100 I should have got five
less for $1.20.” Can you say what was the price per 100?

Answered question
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Let's assume that the price per 100 apples is x¢ and the man bought y apples
 then we have 
   eq. 1) as x*y = 1.2$
   Man said, if the price per 100 was 4¢ more, then he could have had 5 less from what 
he bought, thus
 eq. 2) - (x+4)*(y-5) = 1.2$
     x is in cents in both the equations and the price x is per 100 apples, so 
updated equations become
   x        y
  __    x   ___   = 1.2             --------(1)
   100     100 
     
(x+4)      (y-5)
____   x  _____  = 1.2             --------(2)
 100        100 
   Solving equations 1 and 2 
 eq(1) => xy = 12000 => y=12000/x ---- (3)
   Solving equation 2 we get, xy-5x+4y-20 = 12000
 Substituting xy=12000 in above equation
 => -5x+4y = 20
  Again substituting y=12000/x in above equation, 
 -5x+48000/x = 20, dividing both sides by 5
 -x+9600/x = 4 => x^2+4x-9600 = 0 => (x+100)(x-96) = 0 
 this gives 2 solutions
 x=96 and x=-100
 Discarding -ve value of 100
   Final answer, man bought, 100 apples for 96 cents.

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