Question

A part of monthly hostel charges is fixed and the remaining depends on the
number of days one has taken food in the mess. When a student A takes food for
20 days she has to pay Rs 1000 as hostel charges whereas a student B, who takes
food for 26 days, pays Rs 1180 as hostel charges. Find the fixed charges and the
cost of food per day

IN CROSS MULTIPLICATION METHOD​

Answer 1

let the fixed charge be x and food be y. Then,

x+20y=1000------(1)

x+26y=1180------(2)

x+20y-1000=0----------(3)

x+26y-1180=0----------(4)

x/{20*(-1180)}-{26*(-1000)}

=y/{1*(-1180)}-{1*(-1000)}

=1/(1*26)-(1*20)

x/{-23600-(-26000)} = y/{-1180-(-1000)} = /(26-20)

x/2400 = y/-180 = 1/6

now,

x/2400=1/6 and y/-180=1/6

x=2400/6 and y=-180/6

=400 =30