How many mL of a 17.5% w/v solution of calcium chloride must be mixed with a 5% solution to prepare 360 mL of a 15% solution?

Step 1. Set up alligation. 17.5% (High) 5% (Low) 15% (Target) Step 2. Determine parts. Parts of 17.5% = 15 - 5 = 10 parts Parts of 5% = 17.5 - 15 = 2.5 parts Total parts = 10 + 2.5 = 12.5 parts Step 3. Calculate the volume of 17.5% solution needed for 360 mL. Volume = (10 / 12.5) x 360 = 288 mL