Primary School Math Problem Salt water weighs 25 kg and contains 20 salt After adding some water, sa

The brine weighs 25 kg and contains 20% saltAfter adding some water, the salt content is 8%, ask how much water is added?

It's a question of concentration change. The key to solving this kind of problem is to analyze what changes and what does not change in the process of concentration change, and then solve the problem through invariants.

In the case of the above question, it is clear that the amount of water in the brine increases, and in the middle, the weight of the salt is constant. So that we can make a fuss with the unchanging salt.

First of all, find the weight of salt is: 25*20% 5 (kg), and these salts are exactly 8% of the weight of salt water after adding water.

Therefore, the weight of the brine after adding water can be obtained: 5 8% kg) Finally, the weight of the added water is: kg).

Solution: First calculate the number of kilograms of salt 25 * (multiplied) 20% = 5 (kilograms) and set the total water x kilograms after adding water.

8%*x=5

x = minus the original water by 25 kg: kg).

Answer: Kilograms of water were added.

25*20% 5 (kg), and these salts are exactly 8% of the weight of the brine after adding water.

Therefore, the weight of the brine after adding water can be obtained: 5 8% kg) Finally, the weight of the added water is: kg).

Solution: Suppose x kg of water is added.

8% (25+x)=25*20% from the title

Solution x=A: Kilograms of water are added.

There are many ways.

The quality of salt before and after adding water remains unchanged, and it can be seen that the mass of the solution after adding water is 25*20% 8%=water added.

The original file has 120 1 (1+5)=20

Water has: 120-20=100

Now staring at the front of the ratio is Kai stupid Qing: 20 + 20:100 = 4:6 = 2:3

The salt water weighs 120 grams, and the ratio of salt to water is 1:5

There are 1+5=6 servings.

120 6 = 20 grams per serving.

There is salt 1 20 = 20 grams.

Water 120-20 = 100 grams to grip slowly.

Add another 20 grams of salt, there are 20 + 20 = 40 grams of salt.

The ratio of salt to water is.

100*10 difference = 10 [grams].

10+5=15 [False Summoning Slippery].

100-10 + 50 = 140 [grams] chain ming.

Answer: The ratio is 3:28

It is 1 to 25 because Liang Chong returned to the oak hunger If he is sentenced to add 2 grams of salt, the salt becomes 4 grams, and the water is still 100 grams. Salt ratio to water is 4 to 100 = 1 to 25

Salt has 200 20% = 40 grams.

Now 40 grams of salt water.

A: Add 120 grams of water.

A brine weighs 200 kilograms, and the weight of salt accounts for 20% of the weight of the brine, so you can know how much salt there is.

After adding some water, the weight of the salt accounts for the weight of the brine.

But in this, the salt is constant.

So there is also salt 40

Then the brine is now :

That is, what is sought.

I forgot how to calculate, it's physics.

20% salt water 25 kg of saline containing 25 kg of teaser salt: 25 * 20% 5kg of salt Lu mu can be equipped with 8% concentration of brine: 5 8%.

Add water later: mountain spikes.

Water needs to be added.

25 20% 8%-25,5 8%-25,,,= kg);

Answer: Kilograms of water were added

25g of brine contains salt, 25 is multiplied by 5, indicating that there is 5g of salt, and it becomes salt after adding water, divided by 5, which is the quality of the brine later, and the salt has not changed here, at this time, as long as you subtract 25 to get the amount of water added later.

25 20 = 125 (kg).

25 8 = kilograms).

kilogram) A: Kilograms of water were added.

15% of the saline brine has 20 * 15% = 3 kg of salt, and the salt concentration of the brine is 20% after adding x kg of salt

From the meaning of the question, we can get (3+x) (20+x) =1 5 to get x=

Check, at this time there should be 3+ kg of salt, the total mass of 20+ salt content is (

A: To achieve a brine concentration of 20%, you need to add kilograms of salt.

The original water content in the brine: 20 (1-15%) = 17 (kg).

After making the concentration of the brine 20%, the brine has: 17 (1-20%) = kg).

So, add salt: kg).

20 (1-15%) 17 (kg).

17 (1-20%) kg).

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