Chalk contains calcium, carbon and oxygen in the ratio 10: 3: 12. Find the percentage of carbon in chalk.
It is given in the question that,
Ratio of calcium, carbon and oxygen = 10: 3: 12
Therefore,
Total = 10 + 3 + 12 = 25
Hence,
Percentage of carbon = 
× 100 %
= 3 × 4 %
= 12 %
18