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Large Numbers Around Us

How big a lakh really is

A page holds a grid of dots, 100 across and 100 down. That is 10,000 dots. How many pages make a lakh?

One page: 100 × 100 dots = 10,000.
Step 1 of 4
  1. One page: 100 × 100 dots = 10,000.
  2. A lakh needs 10 such pages.
  3. A crore needs 1,000 pages — too many to draw!
  4. One dot a second: a lakh takes about a day.

The rule

A lakh needs ten pages of 10,000 dots. A crore needs a thousand pages. Check: 10 × 10,000 = 1,00,000. And 1,000 × 10,000 = 1,00,00,000.

You can also see the size with time. Count one thing each second. A day has 24 hours. An hour has 60 minutes, a minute 60 seconds. So a day has 24 × 60 × 60 = 86,400 seconds. A lakh of seconds is a little more than a day. A crore is 100 lakh. So a crore of seconds is 100 times that: about 116 days.

Tap ten tiles in the lab. Switch between a lakh and a crore.

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This track

  1. 0 Start here
  2. 1 Past the thousands column
  3. 2 Two ways to group the same digits
  4. 3 Reading a large number out loud
  5. 4 Which large number is bigger
  6. 5 Rounding to a place you choose
  7. 6 Estimate before you compute
  8. 7 How big a lakh really is
  9. 8 Round which way?
  10. 9 Estimates on one side of the answer
  11. 10 Quick times 5, 25 and 125
  12. 11 Checkpoint: rounding and quick times
  13. 12 The big picture
  14. 13 Track quiz

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