Ravi sold a pen at 5% profit and a pencil at 10% profit. In the whole transaction he earns a profit of ₹13. If he sold the pen at 5% loss and the pencil at 15% profit he got ₹ 7 as a profit. Find cost price of one pen.

₹ 100

Let cost price of pen = x & Pencil = y

x × \(\frac{5}{100}\) + y × \(\frac{10}{100}\) = 13

 5x + 10y = 1300   ----- (i)

-5x + 15y = 700    ----- (ii) (ATQ)

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25y = 2000

y = 80

5x + 800 = 1300

            x = 100