NCERT Class 6 Solutions: Knowing Your Numbers (Chapter 1) Exercise 1.1 – Part 2
Q2 Place commas correctly and write the numerals:

Seventy–three lakh seventy–five thousand three hundred seven.

Nine crore five lakh forty–one.

Seven crore fifty–two lakh twenty–one thousand three hundred two.

Fifty–eight million four hundred twenty–three thousand two hundred two.

Twenty–three lakh thirty thousand ten.
Solution:
Refer the following table to understand the how commas are placed in the Indian system English system of numbering. After 1000 a comma is placed every 2 digits in Indian system; in English system a comma is placed every 3 digits.
Hindi  Indian figure  Powernotation  International figure  International Names 
one  1  10^{0}  1  One 
ten  10  10^{1}  10  Ten 
one hundred  100  10^{2}  100  One hundred 
one thousand  1,000  10^{3}  1,000  One thousand 
ten thousand  10,000  10^{4}  10,000  Ten thousand 
one lakh (also lac)  1,00,000  10^{5}  100,000  One hundred thousand 
ten lakh  10,00,000  10^{6}  1,000,000  One million 
one crore  1,00,00,000  10^{7}  10,000,000  Ten million 
ten crore  10,00,00,000  10^{8}  100,000,000  One hundred million 
one arab or one hundred crore  1,00,00,00,000  10^{9}  1,000,000,000  One billion 
ten arab  10,00,00,00,000  10^{10}  10,000,000,000  Ten billion 
one kharab  1,00,00,00,00,000  10^{11}  100,000,000,000  One hundred billion 
ten kharab  10,00,00,00,00,000  10^{12}  1,000,000,000,000  One trillion 
one neel  1,00,00,00,00,00,000  10^{13}  10,000,000,000,000  Ten trillion 
ten neel  10,00,00,00,00,00,000  10^{14}  100,000,000,000,000  One hundred trillion 
one padm  1,00,00,00,00,00,00,000  10^{15}  1,000,000,000,000,000  One quadrillion 
ten padm  10,00,00,00,00,00,00,000  10^{16}  10,000,000,000,000,000  Ten quadrillion 
one shankh  1,00,00,00,00,00,00,00,000  10^{17}  100,000,000,000,000,000  One hundred quadrillion 
ten shankh  10,00,00,00,00,00,00,00,000  10^{18}  1,000,000,000,000,000,000  One quintillion 

Seventy–three lakh seventy–five thousand three hundred seven.

Nine crore five lakh forty–one.

Seven crore fifty–two lakh twenty–one thousand three hundred two

Fifty–eight million four hundred twenty–three thousand two hundred two

Twenty–three lakh thirty thousand ten.