CAT Quantitative Aptitude Questions | CAT Percentage Questions - Variables

The question is from CAT Percentages. 2IIMs CAT question bank provides you with CAT questions that can help you gear for CAT Exam CAT 2023. Percentages is an important topic for CAT. Does this question remind you of physics? A material is created using other materials. When the amount of those materials are changed, what will be the overall change?

Question 22: Tensile strength of a material A is a multiple of amount of materials a, b, c, d used. If the amount of material of a, b, c, d are changed by +30%, -30%, -25%, +25% respectively, what will be the overall change in tensile strength of A?

1. No Change
2. +14.68%
3. –14.68%
4. Depends on the initial amount of a, b, c, d

Explanatory Answer

Method of solving this CAT Question from Percentages: When the materials are changed, what can be the overall change?

Since, tensile strength of A = a * b * c * d, If we assume initial tensile strength to be 100, we can apply successive % changes to arrive at the final figure
100 -30% ---> 70 (Any of the change can be carried out first, the result would be same)
70 + 30% ---> 91
91 + 25% ---> 113.75
113.75 – 25% --> ~85.31
Therefore, percent change in tensile strength = -14.68%
Note – This question could have been solved by just looking at the options. As the individual percentage increase and percentage decrease are same, it will effectively result in an overall percentage decrease for sure because any increase by any % will result in a greater subsequent decrease if same % decrease is applied. Similarly, aby % decrease by any % will result in a smaller subsequent increase if same % increase is applied.

The question is " what will be the overall change in tensile strength of A?"
The overall change in tensile strength of A will be -14.68%.

Hence, the answer is -14.68%.

Choice C is the correct answer.