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 in any given number is always whatever is its position in the number.
- Do not use ‘and’ any where 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
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- 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 5 6, 7 8 9 The number is Fifty six thousand, seven hundred and 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 and 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.
