The World of Numbers | Exercise 3.4

Question 5

Find three rational numbers between 3.14153.1415 and 3.14163.1416.

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Solution
Understand the Question
  • Any terminating decimal is a rational number because it can be expressed in the form pq\dfrac{p}{q}, where p,qZp, q \in \mathbb{Z} and q0q \neq 0.
  • To find numbers between 3.14153.1415 and 3.14163.1416, we can append extra decimal digits to 3.141503.14150 so that the resulting values remain strictly less than 3.141603.14160.

Step 1 · Find Three Rational Numbers

Rewrite the given numbers with an additional decimal place: 3.1415=3.141503.1415 = 3.14150 3.1416=3.141603.1416 = 3.14160

Any terminating decimals between 3.141503.14150 and 3.141603.14160 are rational numbers. Three such numbers are: First rational number=3.14151\text{First rational number} = 3.14151 Second rational number=3.14152\text{Second rational number} = 3.14152 Third rational number=3.14153\text{Third rational number} = 3.14153

Answer

3.141513.14151, 3.141523.14152, and 3.141533.14153

Common Mistakes
  • Exceeding the Upper Bound: Appending digits to 3.14163.1416 (e.g., writing 3.141613.14161), which makes the number strictly greater than 3.14163.1416 instead of lying between the two given numbers.
  • Rational vs. Irrational Confusion: Terminating decimals are always rational numbers. Only non-terminating and non-repeating decimals are irrational.

More questions in Exercise 3.4

Q1

Represent the rational numbers 23\dfrac{2}{3}, 54-\dfrac{5}{4} and 1121\dfrac{1}{2} on a single number line.

Q2

Find three distinct rational numbers that lie strictly between 12-\dfrac{1}{2} and 14\dfrac{1}{4}.

Q3

Simplify the expression: (14)+(512)\left(-\dfrac{1}{4}\right) + \left(\dfrac{5}{12}\right).

Q4

A tailor has 153415\dfrac{3}{4} metres of fine silk. If making one kurta requires 2142\dfrac{1}{4} metres of silk, exactly how many kurtas can he make?

Q5

Find three rational numbers between 3.14153.1415 and 3.14163.1416.

Q6

Can you think of other way(s) to find a rational number between any two rational numbers?

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