Question

# A shopkeeper buys some books for Rs. 80. If he had bought 4 more books for the same amount, each book would have cost Rs. 1 less. Find the number of books he bought.                                            ORThe sum of two number is 9 and the sum of their reciprocals is $\frac{1}{2}$. Find the numbers.

Total cost of books = Rs.80

Let the number of books = x

So the cost of each book = Rs $\frac{80}{\mathrm{x}}$

Cost of each book if he buy 4 more books = Rs

As per given in equations:

Since number of books cannot be negative,

so the number of books he brought is 16.

OR

Let the frist number be x then the second number be 9 - x as the sum of both  number is 9.

Now the sum of their reciprocal is $\frac{1}{2}$, therefor

If  x = 6 then other number is 3.

And, if x = 3 then other number is 6.

Hence numbers are 3 and 6.