Question

Chalk contains calcium, carbon and the oxygen in the ratio $10:3:12$. Find the percentage of carbon in chalk.

If in a stick of chalk, carbon is $3g$, what is the weight of the chalk stick.

Answer 1

Step 1: Calculating the percentage of carbon in chalk

Given,

The ratio of calcium, carbon, and oxygen in chalk= $10:3:12$

Now,

The total part of calcium, carbon, and oxygen in chalk= $10+3+12=25$

In this part, the total part of carbon= $\frac{3}{25}$

Percentage of carbon $=\frac{3}{25}\times 100=12\%$

Therefore, the Percentage of Carbon= $12\%$

Step 2: Calculating the weight of Chalk stick

Given,

weight of carbon in chalk= $3\mathrm{g}$

Let us assume the weight of the stick be W,

So $12\%$of W= $3\mathrm{g}$

After calculating we get:

$$\begin{gathered} \frac{12}{100}\times \mathrm{W}=3 \\ \mathrm{W}=3\times \frac{100}{12} \\ \mathrm{W}=1\times \frac{100}{4} \\ \mathrm{W}=25\mathrm{g} \end{gathered}$$

Therefore, The weight of chalk= $25\mathrm{g}$