Summary

We came across large numbers — lakhs, crores and arabs; millions and billions. We learnt how to read and write these numbers in the Indian and American/International naming systems. (a) 1 lakh is 1 followed by 5 zeroes: 1,00,000 (b) 1 crore is 1 followed by 7 zeroes: 1,00,00,000 (c) 1 million is 1 followed by 6 zeroes: 1,000,000 (which is also ten lakhs) (d) 1 arab is 1 followed by 9 zeroes: 1,000,000,000 (which is also 100 crore or 1 billion)

We generally round up or round down large numbers. Many times it is enough just to know roughly how big or small something is.

To get a sense of large numbers or quantities, we can check how many times bigger they are compared to numbers or quantities that are more familiar.

We saw how to factorise numbers and regroup them to make multiplications simpler.

We carried out interesting thought experiments such as  — “Would one be able to watch 1000 movies in a year?”