Q.7 (i) Chalk contains calcium, carbon and oxygen in the ratio 10 : 3 : 12. Find the Percentage of carbon in chalk.
(ii) If in a stick of chalk, carbon is 3 g, what is the weight of the chalk stick?

(i) Sum of the ratio parts = 10 + 3 + 12 = 25
\(\therefore \) Percentage of carbon in chalk
=\(\frac{3}{25} \) ×100%=12%
Hence, the Percentage of carbon in chalk = 12%
(ii) Weight of carbon = 3 g
\(\therefore \)Weight of chalk =\(\frac{3}{3} \) × 25 g = 25 g
Hence, the weight of chalk = 25 g