# Ex 8.3, 7 - Chapter 8 Class 7 Comparing Quantities

Last updated at Nov. 6, 2018 by Teachoo

Last updated at Nov. 6, 2018 by Teachoo

Transcript

Ex 8.3, 7 (i) Chalk contains calcium, carbon and oxygen in the ratio 10:3:12. Find the percentage of carbon in chalk. Calcium : Carbon : Oxygen = 10 : 3 : 12 Total parts = 10 + 3 + 12 = 25 Percentage of carbon = (๐๐๐๐ก๐ ๐๐ ๐๐๐๐๐๐)/(๐๐๐ก๐๐ ๐๐๐๐ก๐ ) ร 100 = 3/25ร 100% = 3 ร 100/25 % = 3 ร 4% = 12% Ex 8.3, 7 (ii) If in a stick of chalk, carbon is 3g, what is the weight of the chalk stick? Given, Weight of Carbon = 3g Now, We know that Carbon 12% of chalk Weight of Carbon = 12% ร Weight of chalk 3 = 12% ร Weight of chalk 3 = 12/100 ร Weight of chalk 12/100 ร Weight of chalk = 3 Weight of chalk = 3 ร 100/12 Weight of chalk = 100/4 Weight of chalk = 25 So, Weight of chalk is 25 g Weight of chalk = 3 ร 100/12 Weight of chalk = 100/4 Weight of chalk = 25 So, Weight of chalk is 25 g

Ex 8.3

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.