Question

Chalk contains calcium, carbon and oxygen in the ratio 10 : 3 : 12.
(a) Find the percentage of carbon.
(b) What will be the actual quantity of carbon (in grams) in one kilogram of chalk?

Answer 1

(i) Given ratio = 10 : 3 : 12

Total part = 10 + 3 + 12 = 25

Part of Carbon =

\frac{3}{25}

25

3

Percentage of Carbon part in chalk = \frac{3}{25}\times100=12\%

25

3

×100=12%

ii) Quantity of Carbon in chalk stick = 3 g

Let the weight of chalk be x g.

Then, 12% of x = 3

=25\ g

100

12

×x=3⇒x=

12

3×100

=25 g