PROPORTIONAL 7 REASONING-1 | Class 8 Mathematics Notes
By ConceptScroll Team · Published on 17 July 2026 · 3 min read
PROPORTIONAL 7 REASONING-1 – this guide gives you a concise, exam-ready overview of PROPORTIONAL 7 REASONING-1 from Class 8 Mathematics, written by ConceptScroll editors and reviewed against the latest NCERT textbook.
Equivalent Ratios
Equivalent ratios are ratios that express the same relationship between quantities, even though the numbers themselves may be different. For example, the ratio 2:3 is equivalent to 4:6 because both represent the same proportional relationship.
This section explains how to generate equivalent ratios by multiplying or dividing both terms of a ratio by the same non-zero number. This process is similar to simplifying or expanding fractions. The concept is crucial because it allows us to compare ratios easily and recognize when two ratios are proportional.
The chapter provides step-by-step methods for finding equivalent ratios. For instance, starting with the ratio 3:5, multiplying both terms by 2 yields 6:10, which is equivalent to the original ratio. Similarly, dividing both terms of 8:12 by 4 gives 2:3, an equivalent ratio in simplest form.
Students learn that equivalent ratios maintain the same relative size or proportion between quantities. This understanding is essential for solving problems involving scaling, resizing, and converting units.
The section also includes examples where students identify equivalent ratios and use them to solve problems, reinforcing the concept through practice.
📊 Diagram: Diagrams illustrate the process of generating equivalent ratios by scaling both terms of a ratio, showing arrows from the original ratio to its multiples and simplified forms.
🧪 Activity: Activity 7.2: Students are given various ratios and asked to find equivalent ratios by multiplying or dividing both terms by different numbers, then verify if the ratios are equivalent using cross multiplication.
🔗 Connection: Understanding equivalent ratios prepares students for the next section on comparing ratios and solving problems involving proportions.
Frequently asked questions
1. Divide ₹4,500 into two parts in the ratio 2 : 3.
Let the two parts be 2x and 3x. Then, 2x + 3x = 4500 => 5x = 4500 => x = 900. So, the two parts are 2900 = ₹1800 and 3900 = ₹2700.
2. In a science lab, acid and water are mixed in the ratio of 1 : 5 to make a solution. In a bottle that has 240 mL of the solution, how much acid and water does the solution contain?
Total parts = 1 + 5 = 6. Volume of acid = (1/6) × 240 = 40 mL. Volume of water = (5/6) × 240 = 200 mL.
3. Blue and yellow paints are mixed in the ratio of 3 : 5 to produce green paint. To produce 40 mL of green paint, how much of these two colours are needed? To make the paint a lighter shade of green, I added 20 mL of yellow to the mixture. What is the new ratio of blue and yellow in the paint?
Total parts = 3 + 5 = 8. Blue paint = (3/8) × 40 = 15 mL. Yellow paint = (5/8) × 40 = 25 mL. After adding 20 mL yellow, new yellow = 25 + 20 = 45 mL. Blue remains 15 mL. New ratio = 15 : 45 = 1 : 3.
4. To make soft idlis, you need to mix rice and urad dal in the ratio of 2 : 1. If you need 6 cups of this mixture to make idlis tomorrow morning, how many cups of rice and urad dal will you need?
Total parts = 2 + 1 = 3. Rice = (2/3) × 6 = 4 cups. Urad dal = (1/3) × 6 = 2 cups.
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