1.7 SUMMARY

“Screen Readable NCERT Class 7 Mathematics Textbook – Ganita Prakash – for Blind and Visually Impaired Students prepared by Professor T K Bansal.”

• We came across large numbers like, lakhs, crores, and arabs; millions and billions. We learnt how to read and write these large numbers in the Indian and in the 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 a 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 to us.

• We saw how to factorize 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?”