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Lesson one 1) Counting numbers : Fifth Primary The Numbers Any numbers you can use for counting things: 1, 2, 3, 4, 5, ……………….. It is usually represented by letter C Notes : Does not include zero or negative numbers or fractions or decimals. Book P. 2 &P. 3
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2) Natural numbers : The counting numbers + zero. It is usually represented by letter N Notes : Does not include negative numbers or fractions or decimals. Remarks: N = the set of counting numbers { 0 }. N – {0}= the set of counting numbers. The set of counting numbers is the set of natural numbers.
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Remember The set of counting numbers = { 1, 2, 3, 4, ……..} or C = { 1, 2, 3, 4, ……..} It is an infinite set The set of Natural numbers = { 0, 1, 2, 3, ……..} or N= { 0, 1, 2, 3, ……..} It is an infinite set The smallest natural number is zero. The smallest counting number is one C N N – {0}= C N ∩ C = C
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Solved Examples 1)Complete by using , , or : A. ɸ ……………….. C B. {12526 } ……………….. N C. 0 ……………….. C D. {1.5 } ……………….. N E. 9.25 + 0.75 ……………….. C A. B. C. D. E. Solution:
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1)Complete by using , , or : A. ɸ ……………….. N B. {0} ……………….. C C. 0 ……………….. C D. {1, 0.5 } ……………….. C E. {125684 }……………….. N 2)Complete :
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3) Put (√) or (×): I. 0.5 is a natural number between 0 and 1 ( ) II. The set of the natural number is finite set ( ) III. 7.5 C ( ) IV. {0 } {1, 2, 3, 4 } =N ( ) Homework Booklet P.1 and P. 2
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