What is 39/20 written as decimal ?

9514 1404 393

  21 3/7 mL ≈ 21.43 mL

Step-by-step explanation:

Let x represent the amount of 6% solution that should be added. The the total volume of sodium carbonate in the mix is ...

  1%(50) +6%(x) = 2.5%(50 +x)

  50 +6x = 125 +2.5x . . . . . multiply by 100, eliminate parentheses

  3.5x = 75 . . . . . . . . . . . . . subtract 2.5x+50

  x = 21 3/7 . . . . . . . . . . . . . divide by 3.5

21 3/7 mL, about 21.43 mL, of 6% solution should be added to make a 2.5% solution.