Answer: Total distance of the swimming competition is 55.56 km.
Explanation:
Let x be the total distance of the swimming competition.
On the first day, Angie covered 25% of the total distance, which means she swam 0.25x km.
On the second day, she covered one-third of the remaining distance, which is (1 - 0.25)x = 0.75x km.
So, she swam (1/3) * 0.75x = 0.25x km on the second day.
On the third day, she covered 25% of the remaining distance, which is (1 - 0.25 - 1/3)x = 0.42x km.
So, she swam 0.25 * 0.42x = 0.105x km on the third day.
On the final day, she swam half of the remaining distance,
which is (1 - 0.25 - 1/3 - 0.5)x = 0.125x km.
The total distance she swam is the sum of the distances swum on each day:
0.25x + 0.25x + 0.105x + 0.125x = 0.73x
We know that the total distance of the competition is x - 15 km (since she still has 15 km left to swim).
So we can set up the equation:
0.73x = x - 15
Solving for x, we get:
x-0.73x = 15
0.27x = 15
x = 55.56
Therefore, the total distance of the swimming competition is 55.56 km.