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NCERT Solutions for Ganita Prakash (Part 1) Chapter 1 Large Numbers Around Us

Updated on 2026-09-05

About this chapter

1 lakh = 1,00,000 (1 followed by 5 zeroes); 1 crore = 1,00,00,000 (7 zeroes); 1 arab = 1,00,00,00,000 (9 zeroes). Indian system groups digits 3-2-2-2 from the right (thousand, lakh, crore); the American/International system groups them 3-3-3 (thousand, million, billion). 1 million = 10 lakh, 1 billion = 100 crore = 1 arab, and 10,000 lakh make one billion. Big numbers become meaningful when you compare them with something familiar — Somu's 40 m building, a 100-year lifetime, the seats in a stadium. Rounding up, rounding down and the five 'nearest neighbours' (nearest thousand, ten thousand, lakh, ten lakh, crore) let you answer questions quickly without exact arithmetic. Regrouping factors makes multiplication easy: ×5 is ÷2 then ×10, ×25 is ×100 then ÷4, ×125 is ×1000 then ÷8. An m-digit

  • –21.1 A Lakh Varieties!
  • .1 A Lakh Varieties!
  • (Getting a Feel of Large Numbers)1.1 A Lakh Varieties!
  • –5Reading and Writing Numbers
  • –61.2 Land of Tens
  • .2 Land of Tens
  • –91.3 Of Crores and Crores!
  • .3 Of Crores and Crores!
  • .4 Exact and Approximate Values
  • (Nearest Neighbours)1.4 Exact and Approximate Values
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Exercises

  1. –21.1 A Lakh Varieties! — In-text Questions Page 1
  2. .1 A Lakh Varieties! — In-text Questions Page 31
  3. .1 A Lakh Varieties! — Figure it Out Page 31
  4. (Getting a Feel of Large Numbers)1.1 A Lakh Varieties! — In-text Questions Page 3
  5. –5Reading and Writing Numbers — In-text Questions Page 4
  6. –61.2 Land of Tens — Land of Tens Page 5
  7. .2 Land of Tens — Figure it Out Page 61
  8. .2 Land of Tens — In-text Questions Page 71
  9. .2 Land of Tens — Figure it Out Page 71
  10. –91.3 Of Crores and Crores! — In-text Questions Page 8
  11. .3 Of Crores and Crores! — Figure it Out Page 91
  12. .4 Exact and Approximate Values — In-text Questions Page 101
  13. (Nearest Neighbours)1.4 Exact and Approximate Values — In-text Questions Page 11
  14. –121.4 Exact and Approximate Values — Estimating Sums and Differences Page 11
  15. .4 Exact and Approximate Values — Populations of Cities Page 131
  16. .5 Patterns in Products — In-text Questions Page 141
  17. .5 Patterns in Products — Figure it Out Page 141
  18. –15 (How Long is the Product?)1.5 Patterns in Products — In-text Questions Page 14
  19. –181.5 Patterns in Products — Fascinating Facts about Large Numbers Page 16
  20. –191.6 Did You Ever Wonder…? — In-text Questions Page 18
  21. –211.6 Did You Ever Wonder…? — Figure it Out Page 19
  22. Puzzle Time — Puzzle Time: Toothpick Digits Page 23
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