Answer:
The juice concentration in the punch that Johan added was 35%.
Explanation:
Since a bottle contains 750mL of fruit punch with a concentration of 50% pure fruit juice, and Johan drinks 100mL of the punch and then refills the bottle with an equal amount of a cheaper brand of punch, if the concentration of juice in the bottle is now reduced to 48%, to determine what was the concentration in the punch that Johan added, the following calculation must be performed:
750 = 100
650 = X
650 x 100/750 = X
65000/750 = X
86,666 = X
86.666 x 0.5 + 13.333 x 0.4 = 0.486662
86.666 x 0.5 + 13.333 x 0.39 = 0.4853287
86.666 x 0.5 + 13.333 x 0.35 = 0.4799955
Thus, the juice concentration in the punch that Johan added was 35%.