How much water should we add to 20 kg of seawater to change its concentration from 3% to 2%?

Question

The answer to the question has to be in kg.

Answer 1

20 kg of 3% salt

3%*20=0.6 kg salt

x=# kg of water to be added

0.6 kg of salt in how much solution is 2% of the solution ?

0.6/(20+x)=2%

0.6/(20+x)=0.02/1

cross multiply

1*0.6=0.02*(20+x)

0.6=0.4+0.02x

0.6-0.4=0.02x

0.2=0.02x

multiply both sides by 100

20=2x

x=20/x

x=10 kg of water must be added

check: 0.6/(20+10)=0.6/30=6/300=1/50=2/100=2%

Answer 2

Hi Franklin!!

 

If 20 kg of seawater contains 3% salt by weight, then,

 

(20 kg) (0.03) = 0.6 kg of salt 

 

then to calculate the mass of the solution that would be 2% in salt

 

(x kg) (0.02) = 0.6 kg of salt

 

Divide 0.6 by 0.02 and the mass of the solution is 30 kg

 

Thus, 10 kg of water was added to the 20 kg of seawater to dilute it from 3% to 2%.

 

 

Hope this helps!!

 

Carol