Water Saving
We know that 7 0 % of earth's surface is covered with water out of which 9 7 % is salt water. But, 7 5 % of the fresh water available is trapped in a form of ice. So, the part of the total earth's surface that actually contains liquid fresh water is given by b a , where a and b are coprime positive integers, find the value of a + b .
SAVE WATER , SAVE LIFE
Inspired by my geography book
The answer is 4021.
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1 solution
So we actually consume water from 4 0 0 0 2 1 t h part of total earth's surface. Isn't it almost negligible? And the worst thing is, its decreasing due to various factors. What will happen after few decades?
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Don't underestimate how much water there really is on earth! A rough estimate is 2 × 1 0 1 8 cubic meters. That leaves 1 0 1 6 cubic meters of available liquid fresh water. With the current population, that means about 1 . 5 ⋅ 1 0 6 cubic meters, or 1.5 billion liters, per member of the population.
Also, don't forget that we not only use water but we also return it back to our environment! We will not soon run out of water. The bigger challenge is not to pollute the water beyond recovery, and not to damage the mechanisms that keep freshwater available to us.
If only "about 75%" is trapped, why can we use the exact fraction 4 3 , as opposed to say 1 0 0 0 0 0 7 5 0 0 1 ?
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Isn't using 4 3 easier than using 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7 5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 ? :P XD
PS I have edited the problem.
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@Nihar Mahajan – Where does 1 from 7 5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 comes from ?
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@Jason Chrysoprase – Cruel Tzar Calvin Lin spotted the word "about" in my problem statement so it can be approximated: 1 0 0 0 0 0 0 0 0 0 0 7 5 0 0 0 0 0 0 0 1 ≈ 7 5 %
This is why in science, where nearly all numerical values are approximate, use decimal notation.
It is also a good reason to ask for a decimal number as an answer, rather than "the sum of coprime numerator and denominator". The function Q + ∋ x = a / b ↦ a + b ∈ N is the opposite of continuous: it is unbounded on arbitrary small intervals. This makes it particularly unsuited for "approximate" situations.
That's a serious problem and when I use washrooms in my school most of the time I find the tap open which hurts me although we are getting water but many aren't. When I ask my friends to close the tap when they leave they just ignore. What's the use of getting marks in geography if you don't apply what you learnt.
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That's true!
I know, i felt the same
It really sad to know people just throwing water, i mean water is precious. I quickly close the tap
SAVE WATERRRR
Current population > > population after decades. :/ I don't know how we are inviting our own destruction , but we have other ways to make water.
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Wait, do you mean Current population << population after decades?
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@Nihar Mahajan – Yeah yeah,i mean that only. Sign convention
@Nihar Mahajan – Edunova's logo:- SAVE WATER. I hope there was some way to make the molarity of impurities and salts in sea water negligible. Else, soon we would be facing a calamity. :(
⎩ ⎪ ⎨ ⎪ ⎧ 1 0 7 → Water on earth 1 0 7 × 1 0 0 3 → Fresh Water on earth 1 0 7 × 1 0 0 3 × 4 1 → Liquid Fresh Water
Liquid Fresh Water : b 4 0 0 0 a 2 1 ⟹ a + b = 4 0 2 1