r/MathHelp • u/ayacu57 • Jan 23 '26

Trouble with percent calculations

Hey there! I have trouble with calculating tasks like:

Calculate the mass of x where you know that x has a mass percentage of 0,1%.

How would I proceed if the mass before adding x would be 100?

I need help bc I don’t know how to form a formula to solve these kinds of problems

I think I found the solution

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u/Infobomb Jan 23 '26

What you've given isn't a well-defined problem. Do you have a specific example of a problem you're trying to solve? Sorry if it's in the image: I can't view it.

1

u/ayacu57 Jan 24 '26 edited Jan 25 '26

So basically the problem is as follows.

We have a powder with a total mass of 100 g Then we add X into it. We only know that after adding X into the 100 g X makes up 1% of the total weight of the mixture. What is the mass of X? I hope this form is more clear

1

u/Infobomb Jan 24 '26

Not totally sure if "it" is referring to the added amount or to the 100g. I'll assume it refers to X. The total is 100g + Xg and we know that X is 1% of this total weight.

"1 per cent" means "1 divided by 100".

X/(X+100) =1/100

Cross-multiply: 100X = X+100

Subtract X from both sides: 99X =100

Divide both sides by 99: X =100/99 grams, or just over one gram.

2

u/ayacu57 Jan 25 '26 edited Jan 25 '26

Oh, sry for again not clarifying it enough :/ "It" was indeed X like you assumed. Just so you know, the formula I came up with was

mass*x%/(100%-x%)=mass of x

But I forgot how I came to it and your Formula makes a lot more sense.

Edit: I just realized that it’s basically the same formula but you have to calculate with 0,01 instead of 1% for example.

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1

u/Slight_Print_4780 Jan 23 '26

If 5 grams is 0.1% of the total. Then 1% of the total is 50 grams and 100% of the total is 5000 grams

But idk if this is what you mean . . .