17. Nils swam a total of 6.48 km in three days. He swam 0.720 km longer on Day 2 than on Day 1. The distance he swam on Day 3 was 3 times the distance he swam on Day 2. How many kilometers did he swim on Day 3?
Let x = Day 1 Day 2 = x + 0.72 Day 3 = (x + 0.72)(3) Total km = 6.48 km 6.48 = x + (x + 0.72) + ((x + 0.72)(3)) 6.48 = x + x + 0.72 + 3x + 2.16 6.48 - 2.16 - 0.72 = 5x 5x = 3.6 x = 0.72 Day 3: (x + 0.72)(3) (0.72 + 0.72)(3) (1.44)(3) 4.32 Nils swam 4.32 km on Day 3.