Question

A scientist mixes water (containing no salt) with a solution that contains 20% salt. she wants to obtain 140 ounces of the mixture that is 15 % salt. How many ounces of water and how many ounces of the 20% salt solution should she use?

Answer 1

the scientist needs to mix 35 ounces of water with 105 ounces of the 20% salt solution to obtain 140 ounces of the mixture that is 15% salt.

Explanation:

Let's call the number of ounces of water that the scientist needs to mix with the salt solution "x". Then, the number of ounces of the 20% salt solution that she needs to use would be 140 - x (because the total amount of mixture is 140 ounces).

Now, we can set up an equation based on the amount of salt in the mixture:

0.15(140) = 0.20(140 - x) + 0(x)

This equation says that the amount of salt in the final mixture (which is 15% of 140 ounces) is equal to the amount of salt in the 20% salt solution plus the amount of salt in the water (which is 0, since water contains no salt).

We can simplify and solve for x:

21 = 28 - 0.2x

0.2x = 7

x = 35

Therefore, the scientist needs to mix 35 ounces of water with 105 ounces of the 20% salt solution to obtain 140 ounces of the mixture that is 15% salt.