Help with a maths calculation please.

[planningaheadtoday]

I keep seeing the obvious but I know it's wrong.

My brother has a company and has received 5litres of hand sanitizer.

It is 2000ml softener mixed with 3000ml alcohol. It's 60% alcohol.

I'm trying to add alcohol (95%) to make it up to 70% volume as that's what he ordered but couldn't get.

How much alcohol should I add?

I originally thought it was around 500ml but my logical brain says no as the amount of softener is too much in the overall product. I think it's closer to 1.5 litres extra!

What do you think? It's hurting my head!

2l

By adding another 2000ml, i.e. 2l, you have a total of 7000ml of solution. and 95% of the 2000ml will give you the 1900ml of alcohol content. 3000+1900 = 4900. so 4900/7000 * 100 = 70%

It’s 1666.666666 I think after a very quick calculation (1667 to nearest ml)

4666/6666 = 69.9%

Oops just seen the previous replies - have I over complicated it 😂 I’m tired and did it quickly using algebra on the back of an envelope! Sorry

Didn’t take into account the 95% bit sorry 😐

so the original 3000ml is 100% alchohol? - that is how you calculate the 60%?

@ruthieness yes, the original is 60% alcohol and 30% softener

60% plus 30% - missing 10%?

@ruthieness the problem I had was the 2000ml of softener. This is unmovable as it's already mixed in.

So I need to add alcohol to the 3000ml already in the mix to end up with a 70% alcohol mix. It's not an extra 10% because of the amount of conditioner.

I think the PP that said 2litres of alcohol at 95% is probably the right answer.

My dad and I came up with 1670ml so did and so did @CanICelebrate but I think our calculation was based on 100% strength alcohol.

Yes @planningaheadtodaymine was would have been correct if you were adding 100% alcohol - that will teach me to read the question carefully (which is what I’m always telling my students 😂)

you said the original was 60% alchohol and 30% softener - my point was where is the other 10%?
was that a typo and you meant 40% softenor?

@ruthieness yes, typo sorry. 40% softener and 60% alcohol in original mix.