Question

A part of monthly expenses of a family is constant and the remaining part varies with the price of wheat. When the rate of wheat is Rs250 a quintal, the total monthly expenses of the family are Rs 1000 and when it is Rs 240 a quintal, the total monthly expenses are Rs980. Find the total monthly expenses of the family, when the cost of wheat is Rs350 a quintal.

• A. Rs $1500$
• B. Rs $2000$
• C. Rs $1200$
• D. Rs $1600$

Answer 1

The correct option is C Rs $1200$

Let $K$ be the constant part of monthly expense

Monthly expense when rate of wheat is $Rs250perquintal=Rs1000$

$\therefore 250a+k=1000$ $\to \left(1\right)$

Here $a$is number of quintals bought by family per month.

Monthly expense when rate of wheat is $Rs240perquintal=Rs980$

$\therefore 240a+k=980$ $\to \left(2\right)$

$\left(1\right)-\left(2\right)\Rightarrow 10a=20\Rightarrow a=2$

$\therefore k=980-480$

$k=500$

$\therefore \text{total monthly expense when rate of wheat is Rs 350 per quintal}=350\left(2\right)+500$

$=Rs1200$