Answer:
25 milliliters of 25% solution and 75 milliliters of 5% solution should be used.
Step-by-step explanation:
Since the druggist has to prepare 100 ml of a 10% solution, but has only 5% and 25% solutions, to determine the proportion of each solution that he must use to prepare the solution with the desired percentage, it is necessary to perform the following calculation:
25 x 1 + 5 x 0 = 25
25 x 0.9 + 5 x 0.1 = 23
25 x 0.8 + 5 x 0.2 = 21
25 x 0.7 + 5 x 0.3 = 19
25 x 0.6 + 5 x 0.4 = 17
25 x 0.5 + 5 x 0.5 = 15
25 x 0.4 + 5 x 0.6 = 13
25 x 0.3 + 5 x 0.7 = 11
25 x 0.2 + 5 x 0.8 = 9
Therefore, the percentage that the druggist must use will be between 20% and 30% of the 25% solution, and between 70% and 80% of the 5% solution, that is:
25 x 0.25 + 5 x 0.75 = 10
Therefore, the druggist should use a 25% solution at 25%, and a 75% solution at 5%: Thus, since 100 x 0.25 is equal to 25, 25 milliliters of 25% solution and 75 milliliters of 5% solution should be used.
, so 
must be less than 6.