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Based On class VIII NCERT Syllabus

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- 1. Rational Numbers Irrational Numbers
- 2. A rational number is a real number that can be written as a ratio of two integers. A rational number written in decimal form is terminating or repeating.
- 3. -8 1.3333… - 3/4 16 1/2 3.56
- 4. An irrational number is a number that cannot be written as a ratio of two integers. Irrational numbers written as decimals are non-terminating and non-repeating.
- 5. Square roots of non-perfect “squares” Pi π √17
- 6. One of the subsets of rational numbers
- 7. Integers are the whole numbers and their opposites. Examples of integers are i. 6 ii. -12 iii. 0 iv. 186 v. -934
- 8. Integers are rational numbers because they can be written as fraction with 1 as the denominator
- 9. Whole numbers one of the subsets of rational numbers
- 10. Whole numbers are rational numbers because they can be written as fraction with 1 as the denominator Examples Of whole numbers: i. 1 ii. 2 iii. 3
- 11. Whole numbers are rational numbers because they can be written as fraction with 1 as the denominator
- 12. Whole Numbers Operation Numbers Remarks Addition 0+7=7+0=7, 2+3=3+2=5 For any two whole numbers a and b, a+b = b+a Addition is commutative. Subtraction 4-6 ≠ 6-4 Subtraction is not commutative Multiplication 2×6 = 6×2 = 12, 4×5 = 5×4 = 20 Multiplication is commutative Division 7÷3 ≠ 3÷7 Division is not commutative
- 13. Integers Operation Numbers Remarks Addition -6+5 = (-1) -7+(-5) = (-12) Addition is commutative Subtraction 7-5 = 2 5-7= (-2) Subtraction is not commutative Division 5÷8 = 5 8 8÷5= 8 5 Division is not commutative Multiplication 5×8 = 40 (-5) ×(-8)= 40 Multiplication is commutative
- 14. Rational Numbers Addition- i. 3 8 +( −5 7 )= 21+(−40) 56 = (−19) 56 ii. −3 8 + (−4) 5 = −15+(−32) 40 = −47 40 Subtraction- i. −5 7 − 2 3 = −5×3−2×7 21 = −29 21 ii. 2 3 − 5 4 ≠ 5 4 − 2 3 We find that subtraction is not commutative.
- 15. Multiplication- i. −7 3 × 6 5 = [ −42 15 ] = 6 5 × [ −7 3 ] So, we find that multiplication is commutative. Division- i. −5 4 ÷ 3 7 = 3 7 ÷ −7 3 ii. −5 4 ÷ 3 7 = −5×7 4×3 = −35 12 = 3 7 ÷ −5 4 3 × 4 7 × −5 = 12 −35 So, we find that division is not commutative.
- 16. Whole numbers- Operation Numbers Remarks Addition 7+(2+5)=(7+2)+5 LHS= 7+(7)=14 RHS= (9)+5=14 So, we find addition is associative with whole numbers. Subtraction 8-(9-11)=11-(9-8) LHS= 8-2=6 RHS= 11-1=10 So, we find subtraction is associative with whole numbers. Division 3÷(2÷9)≠ 9÷(3÷2) LHS= 3÷[ 2 1 × 1 9 ]= 27 2 RHS= 9÷[ 3 1 × 1 2 ]= 18 3 So, we find division is associative with whole numbers. Multiplication 7×(2×5)=(7×2) ×5 LHS= 7×10=70 RHS= 14×5=70 So, we find multiplication is associative with whole numbers.
- 17. Integers Operation Numbers Remarks Addition (-2)+[3+(-4)]=[(-2)+3]+(-4) LHS=(-2)+(-1)=(-3) RHS=1+(-4)=(-3) Addition is associative. Subtraction 5-(7-3)= (5-7)-3 LHS= 5-10= (-5) RHS= (-2)-3= (-5) Subtraction is not associative. Division [(-10)÷2]÷(-5)=(-10)÷[2÷(-5)] LHS=(-5)÷(-5)= (-1) RHS= (-10)÷ 2 −5 =(-25) Division is not associative. Multiplication 5×[(-7) ×(-8)]=[5((-7)]×(-8) LHS=5×56=280 RHS=(-35)×(-8)=280 Multiplication is associative.
- 18. Rational numbers- Addition- −2 3 + 3 5 + −5 6 = −2 3 −7 30 = −27 30 = −9 10 [ −2 3 + 3 5 ] + −5 6 = −1 15 + [ −5 6 ] = −27 30 = −9 10 Addition is associative with rational numbers. Subtraction- −2 3 − −4 5 − 1 2 = 2 3 − −4 5 − 1 2 [ −2 3 − ( −4 5 )] − 1 2 = 22 15 − 1 2 = 29 30 −12 15 − 1 2 = −29 30 ≠ 29 30 Subtraction is associative with rational numbers.
- 19. Division- 1 2 ÷ −1 3 ÷ 2 5 = 1 2 ÷ −1 2 ÷ 2 5 LHS= 1 2 ÷ −1 3 ÷ 2 5 = 1 2 ÷ −1 3 × 5 2 = 1 2 ÷ −1 3 ÷ 2 5 = 1 2 ÷ −1 3 × 5 2 = 1 2 ÷ −5 6 = −6 10 Division is associative with rational number.
- 20. Multiplication- −7 3 × 5 4 × 2 9 = −7 3 × 10 36 = −70 108 = −35 54 ( −3 7 × 5 4 ) × 2 9 = −30 244 Multiplication is associative with rational numbers.

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