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Percentages, mixtures, and alligation form a tightly connected idea cluster on the GMAT. Percentages express a part of a whole on a scale of 100. Mixtures describe the result of combining two or more components. Alligation offers a quick way to handle many weighted average situations within mixtures and percentages. A proper understanding of these ideas is an essential part of any comprehensive GMAT preparation course. This page provides an organized subtopic wise playlist for steady preparation of this concept along with a few worked examples.
Percentage represents the “part out of 100”. To calculate percentage, divide the number (part) by the total (whole) and then multiply the result by 100. That means (part ÷ whole) * 100
Example: 30 out of 50 is (30 ÷ 50) * 100 = 60%
Percentage change shows how a value changes from its start. Use: [(new value – old value) ÷ old value] * 100.
Example: value increases from 50 to 80, change = [(80 − 50) ÷ 50] * 100 = 60% increase.
From 80 to 50, change is 37.5% decrease.
Percentage questions may appear easy at first sight, yet many test takers lose marks due to small misunderstandings in interpretation. A percentage increase or decrease can be handled in just a few seconds if you rely on a direct method instead of spreading the work into long calculations. For instance, a 50% increase does not require fractions or elaborate steps; it simply means the original quantity becomes one and a half times its value. A 20% decrease means the quantity becomes 0.8 times the starting value. Once this pattern is clear, the entire topic shifts from confusing to natural. Equally important is the difference between “increase by” and “increase to,” a distinction that many test takers blur when the pressure of the exam builds. This short video explains the method, shows it solving representative questions, and equips you to apply it in GMAT drills, sectional tests, and your full length GMAT practice tests.
Percentage change questions often seem straightforward, yet they hide traps that can unsettle even well prepared students. The real difficulty lies not in the arithmetic but in the shifting base to which each new percentage applies. A 40% increase followed by a 50% decrease is very different from simply subtracting 10%. Each percentage works on the updated value, not on the original one. This is where many students slip, and this is exactly what the GMAT likes to test. The safest habit is to assume a base value of 100. This keeps the numbers friendly and makes it easy to see how successive percentages build on one another. A 40% decrease after a 40% rise, for example, does not take you back to your starting point but to a smaller value instead (100 → 40% increase gives 140 → 40% decrease brings it down to 84). The following brief video walks you through this idea and demonstrates how it can be tested on the GMAT.
Mixture and solution questions are a staple of aptitude tests and GMAT style quantitative reasoning and deserve a firm place in your GMAT prep. They check how well you can balance percentages, proportions, and overall structure. Their main difficulty lies in the fact that whenever you add or remove one ingredient, the total quantity changes, and with it, the percentage composition shifts as well. If you overlook this, you walk straight into the trap of wrong options. A clear and dependable way to manage these problems is to set up a simple table that captures the content of each component. The short video below clarifies this idea and highlights how the GMAT can test it.
Mixture and ratio based solution questions often seem easy at first, yet they can quickly confuse students who approach them without a clear structure. The safest method is to assume convenient numbers for the given ratios and then use a simple table to track total volume, alcohol content, and water content. This practice reduces errors and keeps each step transparent. For instance, when three solutions are mixed in the ratio 2:3:5, it helps to assume volumes of 200, 300, and 500 liters respectively. Once these values are fixed, applying the given percentage concentrations becomes straightforward, and the absolute amounts of alcohol can be calculated. Adding these quantities and dividing by the total volume gives the overall concentration directly. In this way, such problems train you to handle ratios, percentages, and weighted averages in a calm, structured manner. The following short video makes this idea easy to follow and shows the ways in which it can be tested on the GMAT.
Many students feel confident with weighted average problems on mixtures but begin to struggle when the question is turned around: instead of asking for the final concentration, it asks in what ratio two components must be combined to reach a desired concentration. This is exactly where the idea of alligation becomes powerful. Alligation is a structured technique that removes the need for trial and error. It lets you place the two given concentrations and the target concentration in a simple layout, take the differences, and move directly to the required mixing ratio. For instance, if a 30% solution and an 80% solution are to be blended to create a 50% solution, alligation shows the ratio as 3:2 almost instantly, without long calculations. Questions of this type assess not only your arithmetic but also the clarity and discipline of your method. The brief video that follows lays out this idea clearly and shows how it might be tested on the GMAT.
When mixture questions appear, many students spend extra time wrestling with percentages and ratios. In reality, there is a neat and graceful shortcut known as the rule of alligation. This technique lets you find the required ratio at once when two different strengths are blended to obtain a specific final strength. The idea is simple: place the two given values on either side, write the desired value in between, and then take the diagonal differences. These differences directly provide the ratio of the two components. For instance, if the original values are 2 and 10 and the target is 7, the differences are 5 and 3, which give the ratio 3:5. Approaching problems in this way brings clarity and helps you avoid careless slips, especially when the pressure of the exam is high. The short video below breaks this idea down and demonstrates how it can show up on the GMAT.
Real practice for Percentages, Mixtures, and Alligation problems begins when you work on a software simulation that closely matches the official GMAT interface. You need a platform that shows these word and calculation based questions in a GMAT like layout, lets you engage with the information and answer choices naturally, and provides all the on screen tools and functionalities that you will see on the actual exam. Without this kind of environment, it is difficult to feel fully prepared for test day. High quality Percentages, Mixtures, and Alligation questions are not available in large numbers. Among the limited, genuinely strong sources are the official practice materials released by GMAC and the Experts’ Global GMAT course.
Within the Experts’ Global GMAT online preparation course, every Percentages, Mixtures, and Alligation problem appears on an exact GMAT like user interface that includes all the real exam tools and features. You work through more than 100 such questions in quizzes and also take 15 full-length GMAT mock tests that include several Percentages, Mixtures, and Alligation questions in roughly the same spread and proportion in which they appear on the actual GMAT.
All the best!
