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decimal:relating to or denoting a system of numbers and arithmetic based on the number ten, tenth parts, and powers of ten.
perimeter:the continuous line forming the boundary of a closed geometric figure.
estimating:roughly calculate or judge the value, number, quantity, or extent of.
decimal number:decimal numeral system is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers of the Hindu–Arabic numeral system. The way of denoting numbers in the decimal system is often referred to as decimal notation
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