BijayKru wrote:
A rectangular solid has length, width, and height of L cm, W cm, and H cm, respectively. If these dimensions are increased by x%, y%, and z%, respectively, what is the percentage increase in the total surface area of the solid?
(1) L, W, and H are in the ratios of 5:3:4.
(2) x = 5, y = 10, z = 20
In this question, I am sure any we are eliminating A and B. Could you please help me with opt C ( combining both 1 and 2 ). How it is sufficient?
Hello Bijaykru,
For a moment, let’s forget that this is a question on calculating volume.
Let’s assume that we are discussing different sources of YOUR income.
Let’s say you have 3 sources of income – Salary, income from rent of a house that you have let out AND income from interest on a Deposit you have in a bank. So, effectively, there are three variables that have an effect on your total income, isn’t it?
Let’s assume two cases – your total income 5 years ago and your total income NOW. Clearly, most of these variables would have changed – your salary would have increased, you may have increased the rent of your tenants and the bank might be giving you a higher rate of interest now compared to 5 years ago.
One fine day, your buddy suddenly asks “ Hey Bijaykru, what’s the percentage increase in your total income mate, compared to 5 years ago?”. You do not want to answer this question directly, so you tell him “Look here, I’ll give you some information; based on that, you can calculate the percentage increase yourself”.
You give him information about your salary, rent and interest, 5 years ago in statement I. Can he calculate the percentage increase?
You give him information about how much your salary, rent and interest have increased in statement II. For example, you say “ Hey, my salary increased by 5%, rent by 10% and interest by 20%”. Will he be able to calculate the percentage increase?
Your answers to these questions will tell you why the correct answer is C on the original question. Do let me know if my analogy helped you understand this better.
Hope this helps!
Could you tell me why, if the question was asking about Volume, knowing only x,y, and z would be enough?