Question

A part of monthly expenses of a family is constant and the remaining varies with the price of wheat. When the rate of wheat is Rs.250 a quintal,the total monthly expenses of the family are Rs.1,000 and when it is Rs.240 a quintal, the total monthly expenses are Rs.980.Find the total monthly expenses of the family.

Answer 1

assigning the constant expenses part b, the total expense can be expressed as
total expenses=m(price of the wheat)+b
change shape into
f(x)=mx+b
We have when x=250, f(x)=1000 and when x=240, f(x)=980
i.e. 1000=250m+b and 980=240m+b
Solve those: m=2, b=500
the monthly expenses of the family when the cost of wheat is rs.350 per quintal:
f(350)=2*350+500=1200

Answer 2

Answer:

Let the monthly expenses be x Rs and wheat consumed per month be y quintal.

According to question

x+250y=1000 (1)

x+240y=980 (2)

(1)-(2),

10y=20

y=20÷10

=2

x+240y=980

x+240×2=980

x+480=980

x=980-480

=500

Total Monthly expenses =500Rs

Wheat consumed per month =2 quintal

Monthly expenses of family when cost of wheat is Rs 350=x+350y

=500+350×2

=500+700

=1200Rs