Justin was training for a swimming competition. On Day 1 of his training, he swam 400 m. On Day 2, he swam 0.2 km more than Day 1. For each subsequent training session, he swam a distance of 0.2 km more than the previous training session.
- On Day 8 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 0.2) + 0.4 = 0.4
Day 2: ((2 - 1) x 0.2) + 0.4 = 0.6
Day 3: ((3 - 1) x 0.2) + 0.4 = 0.8
Formula
Distance swam = ((Number of day - 1) x 0.2) + 0.4
Distance swam on Day 8
= [(8 - 1) x 0.2] + 0.4
= 7 x 0.2 + 0.4
= 1.4 + 0.4
= 1.8 km
(b)
Number of days he swam 6 km
= [(6 - 0.4) ÷ 0.2] + 1
= 5.6 ÷ 0.2 + 1
= 28 + 1
= 29
Answer(s): (a) 1.8 km; (b) 29