Ella has 0.5 lbs of sugar. How much water should she add to make the following concentrations? Tell Ella how much syrup she will have in each case for 75% syrup?

To answer this item, let x be the amount of water. The concentration (in % sugar) of the solution is calculated by dividing the amount of sugar by the total amount. That is,

       C = (S/ (S + x))(100%)

Substituting the known values to the equation,

      75 = ((0.5/(0.5 + x))(100%)

The value of x from the equation is 0.167.

Answer: 0.167 lbs of water