480 g solution contains 15% sugar, added 120 g of pure water. What is the concentration of sugar in the last solution?

m (in-va) / m (sol) * 100% = 15%
m (in-va) / m (sol) = 0.15
m (in-va) / 480 = 0.15
m (in-va) = 0.15 * 480 = 72 g or
480 – 100%;
x – 15%
(480 * 15) / 100 = 72g
Add another 120 g of water to the existing mass of the solution. m (sol) = 480 + 120 = 600 g
But the mass of sugar in this new solution remained the same: 72 g.
Let’s find the concentration of sugar in the new solution:
W = m (in-va) / m (sol) * 100 = 72/600 * 100 = 12%
Answer: W = 12%