Solution: Initially, the explorer has $ 25 \times 0.60 = 15 $ successful voyages. After 10 more attempts, the total voyages are $ 25 + 10 = 35 $. With a 68% success rate, total successful voyages become $ 35 \times 0.68 = 23.8 $, which rounds to 24 (since successes are whole numbers). The additional successful voyages are $ 24 - 15 = 9 $. - Portal da Acústica