A shopkeeper earns a profit of Re 1 by selling one pen and incurs a loss of 40 paise per pencil while selling pencils from her old stock.

i) In a particular month, she incurs a loss of Rs 5. In this period, she sold 45 pens. How many pencils did she sell in this period?

ii) In the next month, she earns neither profit nor loss. If she sold 70 pens, how many pencils did she sell?

Given that: - If shopkeeper sells 1 pen she earns Re 1 as profit.

And on selling 1 pencil she incurs 40 paise as a loss.

i) Additional data: - For any particular month,

Number of pens sold = 45

Total profit/loss on selling both pens and pencil = Rs. 5

To find: - Number of pencils she sold in this particular month

Let, Profit as + ve sign and loss as - ve sign

Now, as Profit earned by selling one pen = Re 1

Therefore, Profit earned by selling 45 pens = Rs 45,

Or increase in money hence + sign = + Rs 45

Total loss given = Rs 5,

Or the decrease in money hence – sign = – Rs 5

As given, she incurred loss overall in selling both pens and pencil

Therefore, Total loss = Profit earned + Loss incurred

The loss incurred = Total Loss – Profit earned

= Rs (– 5 – 45)

= Rs (–50)

= –(50100)paise

Tip: - Try to convert a unit of the same items in the same unit. Therefore Rs is changed to paise.

USE 1 Re = 100 paise

Total Loss = – 5000 paise

Now as given, Loss incurred by selling one pencil = 40 paise

Or the decrease in money hence – sign = – 40 paise

So, the number of pencils sold = (Total loss in selling pencils)(loss in selling 1 pencil)

= (–5000) ÷ (– 40)

=

= 120 pencils.

(ii) Additional data: - In the next month, there is neither profit nor loss.

Number of pencils sold: - 70

Now,

Since there is neither profit nor loss

Therefore, Profit earned in selling pen + Loss incurred in pencil = 0

Profit earned in selling pen = – Loss incurred in pencil …… (i)

As given, Profit earned by selling 1 pens = Re 1

Loss incurred by selling 1 pencil = 40 paise (from eq. i)

Loss incurred by selling pencils = Rs 70

Or decrease in money hence, – sign = – Rs 70

= – (70 × 100) paise.

Tip: - Try to convert unit of same items in same unit. Therefore Rs is changed to paise.

USE 1 Rs = 100 paise

Total Loss = – 7000 paise

Number of pencils sold = (Total loss in selling pencils)(loss in selling 1 pencil)

= (–7000) ÷ (– 40)

=

= 175 pencils.