Math Question !

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RRITESH KAKKAR

Joined Jun 29, 2010
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To calculate percentage decrease: First: work out the difference (decrease) between the two numbers you are comparing. Then: divide the decrease by the original number and multiply the answer by 100. If your answer is a negative number then this is a percentage increase.
 

Thread Starter

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
125 gallons of a mixture contains 20% water. What amount of additional water should be added such that water content be raised to 25%?
 

tjohnson

Joined Dec 23, 2014
611
125 gallons of a mixture contains 20% water. What amount of additional water should be added such that water content be raised to 25%?
This is basic math. Out of the 125 gallons of the mixture, 20% is water, so there are 125 * 0.2 = 25 gallons of water.

If we want to raise the water content to 25%, we would need 25% of 125 gallons, which is 125 * .25 = 31.25 gallons of water.

Finding the difference between 25 and 31.25 gallons shows that the amount of water that must be added is 31.25 - 25 = 6.25 gallons.
 

tjohnson

Joined Dec 23, 2014
611
ok, it was so simple.
I was messing with meaning.
Oops, I was forgetting something important. When water is added, the total amount of mixture changes, so the problem is more complicated than I was thinking:
0.2(125) + W_added = 0.25(125 + W_added)
25 + W_added = 31.25 + 0.25W_added
0.75W_added = 6.25​

So the correct answer is actually 6.25 / 0.75 = 8.33 gallons of water. Now if you calculate 25% of the total mixture, it equals (125 + 8.33) * .25 = 33.33 gallons, which is 25 + 8.33, proving that this answer is correct.
 

Thread Starter

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
125 gallons of a mixture contains 20% water. What amount of additional water should be added such that water content be raised to 25%?

125 mixture=water + other
125 mixture=25+ 100
for 25%
The water is 31.25

both are same
25+100=31.25+93.75

not getting it.
 

tjohnson

Joined Dec 23, 2014
611
125 gallons of a mixture contains 20% water. What amount of additional water should be added such that water content be raised to 25%?

125 mixture=water + other
125 mixture=25+ 100
for 25%
The water is 31.25

both are same
25+100=31.25+93.75

not getting it.
Sorry, but you won't get it unless you solve it the way I showed in post #12.
 

Thread Starter

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
125 gallons of a mixture contains 20% water.
so, 25 gallon of water right?
100 gallon mixture

What amount of additional water should be added such that water content be raised to 25%?


so,
31.25 gallon water + 93.75 mixture right?
 

bertus

Joined Apr 5, 2008
20,240
Hello,

Your answer in #8 is wrong.
Again : If 40 is 100 %, how many percent is 10.
10 is a quarter of 40.

Bertus
 

tjohnson

Joined Dec 23, 2014
611
Rritesh, I'm sorry to have to say this, but the solution I posted is simple algebra. I learned how to solve problems like this in Algebra 1.

There are plenty of free resources for learning algebra like Khan Academy that you can use. Members of this forum are willing to help you, but we can't teach you all of algebra.
 
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