Large Numbers Around Us

Reading and writing large numbers in the Indian system (lakhs, crores) and the international system (millions, billions), and rounding and estimating them.

Key ideas

Indian commas: the first comma after 3 digits from the right, then after every 2 digits: 4,56,78,912.
International commas: after every 3 digits from the right: 45,678,912.
Read a number group by group, naming each group: 4,56,78,912 is four crore fifty-six lakh seventy-eight thousand nine hundred twelve.
Rounding to a place: look at the next digit; 5 or more rounds up, less than 5 rounds down.
Estimate by rounding each number first, then work out the rough answer.

Remember

Indian	1 lakh = 1,00,000; 1 crore = 1,00,00,000 = 100 lakh
International	1 million = 1,000,000; 1 billion = 1,000,000,000
Between the systems	10 lakh = 1 million; 1 crore = 10 million; 100 crore = 1 billion

Watch out

Putting Indian commas every 3 digits.
Reading 1 crore as 1 million (it is 10 million).
Rounding by looking at the wrong digit.

Worked example

Write 916751036 with commas in the Indian system and in the international system.

Working: Indian: 3 digits, then groups of 2; international: groups of 3

Answer: Indian 91,67,51,036; international 916,751,036