Question

If 20 books cost ₹ 140, then 35 books cost ₹ and books cost ₹ 91.

• A. 245
• B. 235
• C. 255
• D. 13
• E. 11

Answer 1

Answer: (A), (D)

The correct options are
A 245
D 13

Number of books ∝ Cost

We know that, if two quantities are directly proportional, then the ratio between the two quantities is constant.

$\frac{numberofbooks}{cost}$ = constant

$\begin{array}{cccc}\text{Number of books}& \text{20}& 35& y\\ Cost\left(₹\right)& 140& x& 91\end{array}$

$\frac{20}{140}=\frac{35}{x}=\frac{y}{91}$

$\frac{20}{140}=\frac{35}{x}$

$x=35\times \frac{140}{20}$

$x=₹245$

Similarly we can find the value of y.

$\frac{20}{140}=\frac{y}{91}$

$y=13books$

Therefore, the final table looks like as shown below.

$\begin{array}{cccc}\text{Number of books}& \text{20}& 35& 13\\ Cost\left(₹\right)& 140& 245& 91\end{array}$