# After a mark-up of 40% was added to an item a boy sells it for Rs.35. What was his cost price and how much was his mark-up?

Dec 12, 2016

The cost price is Rs.25 and the markup is Rs.10.

#### Explanation:

The important thing to note here is that you cannot just find 40% of Rs.35 and subtract it.

The boy's cost price represents 100%, onto which 40% is added to give Rs.35.

Therefore Rs.35 represents 140% of the cost price and we need to find the value of the 100% and the 40%.

Using
direct proportion:

$\frac{35}{140} = \frac{x}{100}$

$x = \frac{35 \times 100}{140}$

$x = 25 \text{ } \leftarrow$ this is the cost price.

$35 - 25 = 10 \text{ } \leftarrow$ this is the mark up

Make an equation Let the cost price be $p$

140% xx p = 35

$\frac{140}{100} \times p = 35$

$p = 35 \times \frac{100}{140}$

$p = 25$