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When 40% of a number A is added to another number B, B becomes 125% of is previous value. Then which of the following is true regarding the values of A and B? (a) A > B (b) B > A (c) B =A (d) Either (a) or (b) can be true depending upon the values of A and B.

Darth Vader
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1 Answers1

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For such a question, it is useful to write down what we have in a mathematical way: \begin{equation} 0.4A + B = 1.25B \end{equation} Now, by subtracting $B$ on both sides, \begin{equation} 0.4A = 0.25B \end{equation} Now, as $B = 1.6A$, it must be clear what the answer should be

Maurice
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  • Note the odd case, when B=A=0. – NoChance Jun 08 '19 at 12:56
  • Yes, indeed. Although it is a pretty trivial case, it should not be excluded. – Maurice Jun 08 '19 at 12:57
  • What if numbers are negative..? I think it will show A is greater than B. Right? – Darth Vader Jun 23 '19 at 05:09
  • Don't think so, but that is depending on the context! It depends on what they mean. Consider both A, B to be negative. For instance, let $A = -100, B=-50$. Then, $40%$ of $A$ is still negative 40 $(-40)$. Then, when you add that to something, it will become smaller $(-100-40=-140)$. – Maurice Jun 23 '19 at 14:39
  • Concluding: in the general context, the answer stated above is a correct one, for both positive and negative numbers. You can check that by substituting some values in order to see that it works. However, it depends on the formulation interpretation – Maurice Jun 23 '19 at 14:40