Need my numpty math checked please. Trying to work out the gravity of wort after mixing it with water. I’ve already pitched my yeast so don’t wanna mess with it now and I forgot to take a reading

15 litres of wort with a gravity of 1.070 mixed with 5 litres of water gravity of 1.000

15L plus 5L = 20L

15 divided by 20 times 70 equals 52.5

as the 5L water has a 0 gravity reading multiplying it by 0 its just gunna end up as 0

just add the two results to get 1.052.5

its more about the method than the numbers really i guess. found it online an just wanna make sure that this is the way ya do it

Trevtaowillgetyounowhere said:

Need my numpty math checked please. Trying to work out the gravity of wort after mixing it with water. I’ve already pitched my yeast so don’t wanna mess with it now and I forgot to take a reading

15 litres of wort with a gravity of 1.070 mixed with 5 litres of water gravity of 1.000

15L plus 5L = 20L

15 divided by 20 times 70 equals 52.5

as the 5L water has a 0 gravity reading multiplying it by 0 its just gunna end up as 0

just add the two results to get 1.052.5

I did it a different way, but got the same result.

Volume of final solution: 15+5=20L
Contribution to the final solution from the wort is 15/20 = .75
Contribution to the final solution from the water is 5/20 = .25
Contribution to density of final solution of wort: .75 × 1.070 = 0.8025
Contribution to density of final solution of water: .25 × 1.000 = 0.250
Density of final solution = contribution from wort + contribution from water = .8025 + .250 = 1.0525

My method is a general method of finding the density (gravity) of the final solution of any number of additives: find the relative contributions of the components, multiply each by the density of the component it represents, and add the results.

btm said:

Trevtaowillgetyounowhere said:

Need my numpty math checked please. Trying to work out the gravity of wort after mixing it with water. I’ve already pitched my yeast so don’t wanna mess with it now and I forgot to take a reading

15 litres of wort with a gravity of 1.070 mixed with 5 litres of water gravity of 1.000

15L plus 5L = 20L

15 divided by 20 times 70 equals 52.5

as the 5L water has a 0 gravity reading multiplying it by 0 its just gunna end up as 0

just add the two results to get 1.052.5

I did it a different way, but got the same result.

Volume of final solution: 15+5=20L
Contribution to the final solution from the wort is 15/20 = .75
Contribution to the final solution from the water is 5/20 = .25
Contribution to density of final solution of wort: .75 × 1.070 = 0.8025
Contribution to density of final solution of water: .25 × 1.000 = 0.250
Density of final solution = contribution from wort + contribution from water = .8025 + .250 = 1.0525

My method is a general method of finding the density (gravity) of the final solution of any number of additives: find the relative contributions of the components, multiply each by the density of the component it represents, and add the results.

your method is much easier to see where what came from where.

Thanks!

Trevtaowillgetyounowhere said:

Need my numpty math checked please. Trying to work out the gravity of wort after mixing it with water. I’ve already pitched my yeast so don’t wanna mess with it now and I forgot to take a reading

15 litres of wort with a gravity of 1.070 mixed with 5 litres of water gravity of 1.000

15L plus 5L = 20L

15 divided by 20 times 70 equals 52.5

as the 5L water has a 0 gravity reading multiplying it by 0 its just gunna end up as 0

just add the two results to get 1.052.5

Yeah your method is fine, but your explanation would have been clearer if you didn’t say water has 1.000 gravity and then say it has 0 gravity.

fair call