## NUMBER SENSE - ESSENTIAL POINTS

• The place value of a digit in a number is the value it holds at the place in the number. If 2 is at hundred-place in a number, its place value will be 200, if 5 is at thousand-place, its value will be 5000 etc.
• The face value of a digit is the digit itself, at whatever place it may be. It is unchangeable and definite.
• Place value changes according to the digit’s place but face value does not.
• The place value of the digit decreases by tens as it moves from left to right. For instance the place value of the digit 4 in the number 14,560 is 4,000. When it is shifted to 15,460 the place of the digit 4 is now 400.
• In Indian Number System, we use different periods like onesthousands,lakhscrores, etc.
• 1 = One
• 10 = Ten
• 100 = Hundred
• 1,000 = One thousand
• 10,000 = Ten Thousand
• 1,00,000 = One lakh
• 10,00,000 = Ten lakh
• 1,00,00,000 = One crore
• The Indian numbering system uses seperators differently from the international norm; a comma divides every two rather than every three digits to the left of the last three, t
• For Example 5,00,000, 12,12,12,123
• International system is followed by most of the countries of the world. In this system, a number is split up into groups or periods.In the Inter-national System of Numeration, we use ones, tens, hundreds, thousands, millions and billions
• 1 = One
• 10 = Ten
• 100 = Hundred
• 1,000 = One thousand
• 10,000 = Ten Thousand
• 1,00,000 = Hundred Thousand
• 10,00,000 = One Million
• 1,00,00,000 = Ten Million

The 1st period consists of ---> ones, tens and hundred.

The 2nd period consists of ---> thousand, 10 thousand and 100 thousands.

The 3rd period consists of ---> million, 10 million and 100 million.

The 4th period consists of ---> billion, 10 billion and 100 billion.

• 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.
• For example, the Roman numeral for 395 is CCCXCV.
• Large numbers are needed in many fields. It may be calculation of number of students in a school, population census of a city, ascertainment of profits of big corporate houses etc.
• Estimation: At many a times we do not need the exact quantity or numbers, but only an estimate. For instance it could be the number of spectators watching cricket match, an estimate of the number of hair on the head etc.