# (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 3g, what is the weight of the chalk stick?

**Solution:**

Parts of carbon = 3

and sum of all parts = 10 + 3 + 12 = 25

Percentage of carbon = (Parts of carbon / Sum of all parts) × 100

= 3 / 25 × 100

= 12%

(ii) Carbon in the stick of chalk = 3 g,

and carbon percentage in chalk is 12%.

This means 12% of carbon = 3 g

Let total quantity be Q

that is 12/100 × Q = 3

Total Quantity= (3 × 100/12) = 25 g

**Video Solution:**

## (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 3g, what is the weight of the chalk stick?

### Class 7 Maths NCERT Solutions - Chapter 8 Exercise 8.3 Question 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 3g, what is the weight of the chalk stick?

i) Percentage of carbon in chalk is 12%, ii) the Weight of the chalk stick is 25 g.