# A certain group of students uses internet service for a monthly charge of Rs 4,800 . If 4 more students join the group , each person would pay Rs 200 less. Find the number of students in the group in the beginning.

2
by shivam2000

2015-03-13T13:28:14+05:30

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Let the number of students is x and per student pay Rs. y per month
so
x*y = 4800 ------------(1)
as 4 more students join and each pay 200 less
so
(x+4)(y-200) = 4800
x*y - 200x + 4y - 800 = 4800
put the value of x*y from the (1) equation
4800 - 200x + 4y - 800 = 4800
50x - y - 200 = 0
y = 50x + 200 -------------(2)
put the value of y from (2) equation in the (1) equation
x(50x + 200) = 4800
50x² + 200x = 4800
x² + 4x - 96 = 0
x² + 12x - 8x - 96 = 0
x(x + 12) - 8(x + 12) = 0
(x+12)(x-8) = 0
x+12 = 0
x = -12
or
x-8 = 0
x = 8
as the number of students can not be negative
so
at the beginning number of students = 8
and per students pay
8*y = 4800
y = Rs. 600   in the beginning