Easy Ways to Solve Ratio and Proportion in GMAT

    Sayantani Barman Sayantani Barman
    Study Abroad Expert

    Ratio and proportion is a topic which has marked its presence for a long time during school days. In fact, during high school time, this topic has covered the syllabus quite a bit. If you are thinking that in GMAT quant section you won’t come across this, then sorry to disappoint you because this is among the frequent topics. But one thing we can assure is – you can actually score really high in the GMAT quant section if you follow a few of the following tips mentioned. 

    Ratio and Proportion – An introduction

    Let us take a school, for example, there are three kinds of playgrounds – round, rectangle, and square and they are in a proportion of 3:8:4. Suppose we need the information of what percent the round playground makes of the whole or the ratio of the round one to the whole – all these are parts of ration information. We can calculate these from the ratio information itself. 

    A very simple way to understand ratio is to break them in ‘parts’. What does it mean? Well, by this it is meant that for every 3 parts of the round playground, there are 8 parts of the rectangle playground and 4 parts of the square playground. To find the whole portion, simply add up 3+8+4=15 and that is what the whole. We need to know that we have no clue about the actual size of the population. We can further the use of the information provided by saying the round ground to the whole is 3/15, rectangle ground to the whole of 8/15, and square ground to the whole of 4/15. To break it down we can say that the round playground is 1/5 of the whole or 20%.

    In the same manner, if in of the classrooms there are 4 girls out of 7 then we can assume that there are 3 boys. Therefore, we can say that girls are 4/7, and boys are 3/7 and so the ratio of girls to boys is 4:3.

    Explanation with an example of GMAT Ratio and Proportion

    A face wash contains a solution of different mixtures. The ratio of soap to water is 3:2, and the ratio of soap to vitamin E is three times this ratio. The face wash is poured in a plate and left under the sun after half an hour the ratio of water to soap is evaporated partially. Now, what is the ratio of water to vitamin E is in the face wash?

    Solution: firstly, the easiest way to solve this is to break them down obviously, and to do that let us initiate with 3:2. 

    Water – 3

    Soap - 2

    The ratio of soap to vitamin E is three-time this ratio. So first let’s convert the ratio to a fraction and then perform the arithmetic function.


    3/2 * 3= 9/2

    So now, 

    Soap – 9

    Vitamin E – 2

    At this point, we need to recollect one information from the question. The face wash was poured in a plate from which the ratio of water to soap has been partially evaporated. This means the ratio of water to soap is to be halved. So it’s –

    3:2 = 3/2

    3/2 * ½ = ¾

    ¾ = 3:4

    And now,

    Water – 3

    Soap – 4

    And the ratio of soap to vitamin E remains –

    Soap – 9

    Vitamin – 2

    By this time we can notice three different entities having two different ratios. To ease the process let us take them all in one single table and deal with it as a combined ratio. 

    Witness that the soap is common to both ratios, so if the soap had the same ratio value for both, we can pen down the ratio on one line.

    To proceed with this let us make the soap common and then one number is 9 and the other one is 4 – we can convert them to a common value of 36 or you can take any multiple of 4 and 9. Thereby,

    WaterVitamin E
    X 9 =X 9 =
    SoapVitamin E
    X 4 =X 4 =

    With soap now proceeding with a common value of 36, we can put the three-part ratio as follows:

    WaterSoapVitamin E

    Now when it is almost done, the last question which needs to be solved is – at that time, what is the ratio of water to vitamin E?

    We can rightly say that is – 27:8 

    Eventually, we can conclude with a few of the points that will help you students understand and most importantly remember the discussed GMAT preparation tips.

    Firstly, one needs to structure and organize the initial ratios. As we have shown that dividing and sorting the ratios will help one in the long run and will result in a higher GMAT score. A table, in that case, helps the students sort them properly.

    Secondly, work out on the reduction or expansion of the arithmetic operations beforehand to avoid any further complications appearing in the quant section of GMAT. The more you resolve these operations the easier it will be for you to further with it.

    Thirdly, constructing a table and drawing out the combined ratios of the three components in a sum will help one to categorize the components in it. This will even be helpful to the eyes and also faster for the student to solve. Always remember, if you put the right digit in the right place then nothing can go wrong.

    Fourthly and lastly, now when you have listed all the components in the tables drawn out gradually proceed with the step by step questions. And eventually, you will notice that finding the main answer becomes so easy. 



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