The price of 10 chairs is equal to that of 4 tables. The price of 15 chairs and 2 tables together is $₹ 4000$. The total price of 12 chairs and 3 tables is
(a)₹ 3500
(b)₹ 3750
(c)₹ 3840
(d)₹ 3900
Answer
Answer (as printed): D
Explanation
Let the cost of a chair and that of a table be ₹ $x$ and ₹ $y$ respectively. Then, $10 x=4 y$ or $y=\frac{5}{2} x$. $$\begin{aligned} \therefore 15 x+2 y & =4000 \Leftrightarrow 15 x+2 \times \frac{5}{2} x \\ & =4000 \Leftrightarrow 20 x=4000 \Leftrightarrow x=200 . \end{aligned}$$ So, $y=\left(\frac{5}{2} \times 200\right)=500$. $$\begin{aligned} & \therefore \text { Cost of } 12 \text { chairs and } 3 \text { tables }=12 x+3 y \\ & =₹(12 \times 200+3 \times 500)=₹(2400+1500) \\ & =₹ 3900 . \end{aligned}$$
Explanation as extracted from the printed page; notation may be imperfect.