Grade 8 The Number System Practice โ€” Easy

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Question 1 of 26: Which number is irrational?

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Answer key for parents & teachers (26 questions)
  1. Which number is irrational? โ€” โˆš7. โˆš7 โ‰ˆ 2.6457โ€ฆ never terminates or repeats. โˆš9 = 3 is rational, as are 0.25 and โˆ’3/4.
  2. Which of these is a rational number? โ€” โˆš16. โˆš16 = 4, a whole number, so it is rational. The others cannot be expressed as p/q.
  3. Is 0.666โ€ฆ (0.6ฬ„) rational or irrational? โ€” Rational โ€” it is a repeating decimal. Repeating decimals are always rational. 0.666โ€ฆ = 2/3.
  4. Which statement best defines a rational number? โ€” A number that can be written as p/q where p and q are integers and q โ‰  0. The definition of rational is expressible as the ratio of two integers with a nonzero denominator.
  5. The number ฯ€ is irrational because: โ€” Its decimal expansion never terminates and never repeats. Irrationality is defined by the decimal behavior: non-terminating and non-repeating.
  6. Which of these square roots is rational? โ€” โˆš49. โˆš49 = 7, a whole number. The others are not perfect squares.
  7. Between which two integers does โˆš30 lie? โ€” 5 and 6. 5ยฒ = 25 < 30 < 36 = 6ยฒ, so 5 < โˆš30 < 6.
  8. Which of the following is NOT a perfect square? โ€” 50. 50 = 2 ร— 25 is not a perfect square (โˆš50 is irrational). The others equal 5ยฒ, 10ยฒ, 12ยฒ.
  9. Between which two consecutive integers does โˆš10 lie? โ€” 3 and 4. 3ยฒ = 9 < 10 < 16 = 4ยฒ, so 3 < โˆš10 < 4.
  10. Between which two consecutive integers does โˆš45 lie? โ€” 6 and 7. 6ยฒ = 36 < 45 < 49 = 7ยฒ, so 6 < โˆš45 < 7.
  11. Approximate โˆš2 to the nearest tenth. โ€” 1.4. 1.4ยฒ = 1.96 and 1.5ยฒ = 2.25. Since 1.96 is closer to 2 than 2.25 is, โˆš2 โ‰ˆ 1.4.
  12. Which statement about โˆš20 is correct? โ€” โˆš20 is between 4 and 5. 4ยฒ = 16 < 20 < 25 = 5ยฒ, so 4 < โˆš20 < 5.
  13. What is the best first step to approximate โˆš75? โ€” Find the perfect squares on each side: 8ยฒ = 64 and 9ยฒ = 81. The squeezing method always starts by identifying the consecutive perfect squares that bound the radicand.
  14. โˆš3 is approximately: โ€” 1.73. 1.73ยฒ = 2.9929 โ‰ˆ 3. The correct approximation of โˆš3 is about 1.732.
  15. What does "squeezing" mean when approximating โˆšn? โ€” Finding perfect squares that bound n, then narrowing the interval. The squeezing method locates two values whose squares straddle n, then iteratively narrows the interval.
  16. Approximate โˆš99 to the nearest integer. โ€” 10. 10ยฒ = 100, so โˆš99 is just under 10. โˆš81 = 9 and โˆš100 = 10, and since 99 is much closer to 100, the nearest integer is 10.
  17. Why can we not express โˆš5 as a finite decimal? โ€” โˆš5 is irrational โ€” its decimal expansion never terminates or repeats. Irrational numbers, by definition, cannot be expressed as terminating or repeating decimals.
  18. Which property is shown by: 3 + 7 = 7 + 3? โ€” Commutative property of addition. Swapping the order of addition illustrates the commutative property: a + b = b + a.
  19. What is the additive identity for real numbers? โ€” 0. a + 0 = a for any real number a. Zero is the additive identity.
  20. What is the multiplicative identity for real numbers? โ€” 1. a ร— 1 = a for any real a. One is the multiplicative identity.
  21. Which property is shown by: (2 + 3) + 4 = 2 + (3 + 4)? โ€” Associative property of addition. Regrouping without changing order illustrates the associative property: (a + b) + c = a + (b + c).
  22. The additive inverse of โˆ’5 is: โ€” 5. The additive inverse of a is โˆ’a. The additive inverse of โˆ’5 is โˆ’(โˆ’5) = 5, since โˆ’5 + 5 = 0.
  23. The multiplicative inverse of 3/4 is: โ€” 4/3. The multiplicative inverse (reciprocal) of 3/4 is 4/3, since (3/4)(4/3) = 1.
  24. Which expression demonstrates the distributive property? โ€” 4(x โˆ’ 2) = 4x โˆ’ 8. Distributing 4 over (x โˆ’ 2) gives 4x โˆ’ 8. The others show commutative, associative, and identity properties.
  25. Which of these is an example of the commutative property of multiplication? โ€” 5 ร— โˆš3 = โˆš3 ร— 5. Swapping the order of factors shows commutativity: a ร— b = b ร— a.
  26. If (a + b) + c = a + (b + c), which property is this? โ€” Associative property of addition. Regrouping addends without reordering them is the associative property.