Question

Cost of $10$ pens is thrice cost of two notebooks. Cost of one notebook and $5$ pens is $60$ rupees.
What is the cost of $7$ pens ?

• A. $30$
• B. $77$
• C. $63$
• D. $70$

Answer 1

The correct option is C $63$

Let cost of pen be $Rs.x$

and cost of notebook be $Rs.y$

Now, According to question,

$10x=3\times 2y$

$\Rightarrow 10x=6y$

$\therefore y=\frac{10x}{6}$ ...........(i)

And,

$y+5x=60$

$\Rightarrow y=60-5x$ ...........(ii)

From (i) and (ii)

$60-5x=\frac{10x}{6}$

$\Rightarrow 60-5x=\frac{5x}{3}$

$\Rightarrow 180-15x=5x$

$\Rightarrow 180=20x$

$\therefore x=9$

Cost of $7$ pen $=7\times 9=63$