Place value
Every digit in a number has its place value.
Place value is the value represented by a digit in a number on the basis of its position in the number. Each number keeps this order of positions:
1783645: 549
The place value of a digit increases by 10 times for every position we move left, e.g.:
2973:
place value of 3 is 3
place value of 7 is 7×10=70
place value of 9 is 9×10×10=900
place value of 2 is 2×10×10×10=2000
Due to this we can write every number in expanded form:
$$2973=$$
$$3×1+7×10+9×100+2×1000$$
This system of number notation is called decimal system because it uses 10 digits (0, 1, 2 ... 9) to express numbers. Each place value in a number is a power of $10: 10^0 (=1)$, $10^1 (=10)$, $10^2 (=100)$, $10^3 (=1000)$, $10^4 (=10000)$, etc.
$$2973=$$
$$3×10^0+7×10^1+9×10^2+2×10^3$$
