Question

What is the cost of $3$ quintals $20$ kg of coal if $3$ quintals cost Rs. $3900$?

Answer 1

The cost of $3$ quintals coal is $3900Rs$

So, The cost of $1$ quintal coal is $=\frac{3900\times 1}{3}$

$=1300Rs$ --------- $\left(1\right)$

here $1$ quintal $=100kg$

So, $100kg$ coal costs $1300Rs$

So, $1kg$ coal costs

$=\frac{1300\times 1}{100}=13Rs$ --------- $\left(2\right)$

Now,

$3$ qunital $20kg$ costs

$\Rightarrow \left(1300\right)\times 3+\left(13\right)\times 20$

(From $\left(1\right)$ & $\left(2\right)$)

Costs $=3900+260$

Costs $=4160Rs$

$\to$ cost of $3$ quintals $20kg$ of coal is $4160Rs$