Luis was training for a swimming competition. On Day 1 of his training, he swam 400 m. On Day 2, he swam 0.4 km more than Day 1. For each subsequent training session, he swam a distance of 0.4 km more than the previous training session.
- On Day 9 of his training session, how far did he swim? Give your answer in km.
- On which day did he swim a distance of 6 km?
(a)
1000 m = 1 km
400 m = 0.4 km
Pattern for the distance swam
Day 1: ((1 - 1) x 0.4) + 0.4 = 0.4
Day 2: ((2 - 1) x 0.4) + 0.4 = 0.8
Day 3: ((3 - 1) x 0.4) + 0.4 = 1.2
Formula
Distance swam = ((Number of day - 1) x 0.4) + 0.4
Distance swam on Day 9
= [(9 - 1) x 0.4] + 0.4
= 8 x 0.4 + 0.4
= 3.2 + 0.4
= 3.6 km
(b)
Number of days he swam 6 km
= [(6 - 0.4) ÷ 0.4] + 1
= 5.6 ÷ 0.4 + 1
= 14 + 1
= 15
Answer(s): (a) 3.6 km; (b) 15