If the cost of pins reduces by rs 4 per dozen,12 more pins can be purchased for rs 48.The cost of pins per dozen after reduction is?

• 3 dozen @ Rs 16 per dozen means 3*16= 48
  4 dozen @ Rs 12 per dozen means 4*12=48
  
  So after reduction, Cp per dozen is Rs 12 per dozen.
• 12 years agoHelpfull: Yes(2) No(1)
• let cost price per pin = x rs
  prince of a dozen pin = 12x rs
  and pins purchased initially= y
  so we can x*y=48------(1)
  y=48/x----(2)
  now according to question
  new price = 12x-4 (reduce 4 rs per dozen)
  now price per pin-= (12x-4)/12 rs
  at this price we can buy 12 more pins
  means pins purchased= y+12
  so {(12x-4)/12}*(y+12)=48---------(2)
  12xy/12 - 4y/12 + 144x/12 - 4 =48
  12xy - 4y + 144x - 48 = 48*12
  put value of xy from equation 1 and value of y from 2
  we get
  12*48 - 4(48/x) + 144x - 48*12 = 48*12
  on solving above equation we get
  x=1.33
  so price of 1 dozen = 12*1.33 = 15.96
  reduce 4 rs from 1 dozen= 11.96
  price per dozen after reduction = 11.96 rs
  =12 (approximately)
• 12 years agoHelpfull: Yes(0) No(0)
• let cost per dozen be =x
  No. of pins purchased in Rs 48 =48*12/x -------------------(equation 1)
  New cost per dozen is= x-4
  No. of pins purchased will be=48*12/x-4 --------( equation 2)
  Now,
  equation 2 - equation 1 ,
  48*12/x-4 - 48/x = 12
  Solv it we get
  (x)square -4x-192=0
  (x)square -16x+12x-192=0
  x(x-16)+12(x-16)=0
  x=16,x=-12
  so x=16
  new price is x-4, so 16-4= 12
  
• 9 years agoHelpfull: Yes(0) No(0)