Whole Numbers

Whole Numbers

1. Rounding and Estimating

   • To round a number, cut the number at required place
   • Less then 5, round down
   • More than 5, round up
   • e.g. 8470 to nearest hundred
     • 8470 ≈ 8500
   • 3.01

2. Multiplying numbers

   • 2.4.8:Double once, twice or thrice
   • 5: x10 then half
   • 9: x10 then- number
   • 10: add 0
   • 100: add 00
   • 3.02

3. Dividing Numbers

   • 2,4,8: Half once, twice or thrice
   • 5: Divide by 10, then half
   • 10: Delete 0
   • 100: Delete 00
   • 3.03

4. Divisibility Tests

   • 2: Its even
   • 3: sum of digits divisible by 3
   • 4: Last 2 digits divisible by 4
   • 5: number ends in 0 or 5
   • 6: number is divisible by 2 + 3
   • 10: number ends in 0
   • 8: last 3 digits divisible by 8
   • 9: Sum of digits divisible by 9

5. Long Division

   • E.g.

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