krit.club logo

Rational Numbers - Equivalent Rational Numbers

Grade 7CBSE

Review the key concepts, formulae, and examples before starting your quiz.

๐Ÿ”‘Concepts

โ€ข

A rational number is defined as a number that can be expressed in the form pq\frac{p}{q}, where pp and qq are integers and qโ‰ 0q \neq 0. Visually, if you look at a number line, rational numbers fill the gaps between integers, representing parts of a whole.

โ€ข

Equivalent rational numbers are different representations of the same value. For example, on a number line, the fractions 12\frac{1}{2}, 24\frac{2}{4}, and 48\frac{4}{8} all point to the exact same spot halfway between 00 and 11.

โ€ข

To find an equivalent rational number, you can multiply both the numerator and the denominator by the same non-zero integer. Visually, this is like taking a shaded region of a rectangle and dividing every part into smaller, equal pieces; the total shaded area remains the same.

โ€ข

You can also find equivalent rational numbers by dividing both the numerator and the denominator by their common divisor. This process is often called 'simplifying' or 'reducing' the fraction to its lower terms.

โ€ข

A rational number pq\frac{p}{q} is in its standard form if the denominator qq is a positive integer and the numerator pp and denominator qq have no common factor other than 11. In a diagram, this represents the most basic way to express that specific ratio.

โ€ข

Two rational numbers ab\frac{a}{b} and cd\frac{c}{d} are equal if and only if aร—d=bร—ca \times d = b \times c. This is known as the cross-multiplication test for equivalence. If you visualize two proportional rectangles, the product of the extremes equals the product of the means.

โ€ข

Every rational number has an infinite number of equivalent rational numbers. You can keep scaling the numerator and denominator by any integer mโ‰ 0m \neq 0 to generate a new version of the same value.

๐Ÿ“Formulae

General form of a rational number: pq,qโ‰ 0\frac{p}{q}, q \neq 0

Equivalent by multiplication: pq=pร—mqร—m\frac{p}{q} = \frac{p \times m}{q \times m} (where mโ‰ 0m \neq 0)

Equivalent by division: pq=pรทmqรทm\frac{p}{q} = \frac{p \div m}{q \div m} (where mm is a common divisor and mโ‰ 0m \neq 0)

Condition for equality: ab=cdโ€…โ€ŠโŸนโ€…โ€Šaร—d=bร—c\frac{a}{b} = \frac{c}{d} \implies a \times d = b \times c

๐Ÿ’กExamples

Problem 1:

Find three equivalent rational numbers for โˆ’37\frac{-3}{7}.

Solution:

Step 1: Multiply both numerator and denominator by 22: \nโˆ’3ร—27ร—2=โˆ’614\frac{-3 \times 2}{7 \times 2} = \frac{-6}{14} \nStep 2: Multiply both numerator and denominator by 33: \nโˆ’3ร—37ร—3=โˆ’921\frac{-3 \times 3}{7 \times 3} = \frac{-9}{21} \nStep 3: Multiply both numerator and denominator by โˆ’1-1: \nโˆ’3ร—โˆ’17ร—โˆ’1=3โˆ’7\frac{-3 \times -1}{7 \times -1} = \frac{3}{-7} \nTherefore, three equivalent rational numbers are โˆ’614\frac{-6}{14}, โˆ’921\frac{-9}{21}, and 3โˆ’7\frac{3}{-7}.

Explanation:

To find equivalent rational numbers, we multiply the numerator and the denominator by the same non-zero integers (22, 33, and โˆ’1-1). This changes the appearance of the fraction without changing its actual value.

Problem 2:

Check if 410\frac{4}{10} and 1230\frac{12}{30} are equivalent rational numbers.

Solution:

Step 1: Identify the values for cross-multiplication: a=4,b=10,c=12,d=30a=4, b=10, c=12, d=30. \nStep 2: Calculate the product of the numerator of the first and the denominator of the second (aร—da \times d): \n4ร—30=1204 \times 30 = 120 \nStep 3: Calculate the product of the denominator of the first and the numerator of the second (bร—cb \times c): \n10ร—12=12010 \times 12 = 120 \nStep 4: Compare the results. Since 120=120120 = 120, the products are equal.

Explanation:

We used the cross-multiplication method (aร—d=bร—ca \times d = b \times c) to verify equivalence. Since both products are 120120, the two rational numbers represent the same value and are therefore equivalent.