120 gram of solution containing 40% by mass of NaCl are mixed with 200 gram of solution containing 15% by mass NaCl . Determine the mass percent of sodium chloride in the final solution:

If 100 gram of NaCl solution contain 40 gram of NaCl Then 120 gram of same NaCl solution contain 120×40100=48 gram of NaClIf 100 gram of NaCl contain 15 gram of NaCl Then 200 gram of NaCl solution contain 200×15100=30 gram of NaClTherefore total weight of NaCl is 48+30 = 78 gramTotal weight of solution after mixing both solutions is = 120+200 = 320Therefore mass percentage of NaCl is 78/320×100=24.4