NUMBER SENSE - ESSENTIAL POINTS


  • Place Value of a digit=(face value of the digit) X (value of the place)
  • The face value of the digit is same as the number. The face value of the digit 5 in the number 56,789 is 5, the face value of the number 8 is 8. It does not matter where the number is placed. 
  • The place value and the face value of the digit 0 in any given number is always whatever is its position in the number.
  • Do not use ‘and’ anywhere while writing a number name and the name of the period is also not written in plural while writing a number name.
  • The same digits at different places have different place values.
  • Number System : Tth Th H T  O
    • Tth = Ten thousand. The place value of the digit 5 is 5 X 10,000 = 50,000
    • Th = Thousand. The place value of the digit 6 is 6 X 1,000 = 6,000
    • H = Hundred. The place value of the digit 7 is 7 X 100 = 700
    • T = Tens. The place value of the digit 8 is 8 X 10 = 80
    • O = Ones. The place value of the digit 9 is 9 X 1 = 9.
  • In the number 56,789 The number is Fifty six thousand,seven hundred eighty nine. 
  • The number 3,50,876 can also be written as 3,00,000 + 50,000 + 800 + 76 or three lacs, fifty thousand,eight hundred seventy six.
  • One Million = 10,00,000 or 10 lacs.
  • The Roman numerals are as follows –
I V X L C D M
1 5 10 50 100 500 1000
  • The symbol V, L and D are never repeated. Other symbols cannot be repeated more than three times. When we have to write suppose 90, it is ( 100 – 10 ) then for 100 is C and for ten we have to put the symbol X, thus it can be written as XC.
  • Hence the Roman numeral for 900 is CM.
  • The Roman numeral for 78 is LXXVIII
  • Basic rules of Roman numerals
    • In the Roman system there is no symbol for 0
    • Repetition of a Roman numeral means addition
    • A smaller numeral  written to the right of a larger numeral is always added to the larger numeral.
    • A smaller numeral written to the left of a larger numeral is always subtracted from the larger numeral.
    • When a smaller numeral is placed between two larger numerals , then it is always subtracted from the larger numeral immediately following it.

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