# Class 6 Chapter 1 Knowing our Numbers Math Formulas

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Ascending order:-

Arranged in order of smallest to the largest.

For example:-

Ascending order: 90 < 160 < 170 < 185 < 230

Descending order:-

Arranged in order of Greatest to the smallest.

For example:-

Descending order:  235 >195 >180 > 170 > 90

Place Value:-

It refers to the positional value which defines a digits position.

Place Value of a digit in a number = Face Value × Position Value

For example:-

4567

Place value of 5 is 500, place value of 4 is 4000.

Steps to rounding off:-

Step1 – Check the digit of the place right to the place we have to round off.

Step2 – If this digit is greater than or equal to 5 add one to the digit in the left.

Step 3 – If this digit is less than five keep the digit to the left same.

Note:-

• 99 is the greatest 2-digit number.
• 999 is the greatest 3-digit number
• 9999 is the greatest 4-digit number
• 1 million = 10 lakhs
• 10 million = 1 crore
• 100 million = 10 crores
• 1 billion = 100 crores or 1 Arab
• 1 kilometre (km) = 1000 Metres (m)
• 1 Metre (m) = 100 Centimetre (cm)
• 1 Centimetre (cm) = 10 Millimetre (mm)
• 1 Kilogram (kg) = 1000 Grams (gm)
• 1 Litre (l) = 1000 Millilitres (ml)

The roman numerals with the corresponding Hindi – Arabic numerals are:-

 I V X L C D K 1 5 10 50 100 500 1000

Use the following rules to get the values of given roman numerals:-

• If a symbol is repeated, its value is added as many times as it occurs.
• If a symbol of smaller value is written to the right of a symbol of greater value, we add its value to the value of the greater symbol.
• If a symbols V, L and D are never written to the left of a symbol of greater value.
• If a smaller numeral is placed between two larger numeral. It is always subtracted from the larger numeral immediately following it.
• If a bar is placed over a number, it is multiplied by 1000.