Seth was training for a swimming competition. On Day 1 of his training, he swam 800 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 7 of his training session, how far did he swim? Give your answer in km.
- On which day did he swim a distance of 4 km?
(a)
1000 m = 1 km
800 m = 0.8 km
Pattern for the distance swam
Day 1: ((1 - 1) x 0.4) + 0.8 = 0.8
Day 2: ((2 - 1) x 0.4) + 0.8 = 1.2
Day 3: ((3 - 1) x 0.4) + 0.8 = 1.6
Formula
Distance swam = ((Number of day - 1) x 0.4) + 0.8
Distance swam on Day 7
= [(7 - 1) x 0.4] + 0.8
= 6 x 0.4 + 0.8
= 2.4 + 0.8
= 3.2 km
(b)
Number of days he swam 4 km
= [(4 - 0.8) ÷ 0.4] + 1
= 3.2 ÷ 0.4 + 1
= 8 + 1
= 9
Answer(s): (a) 3.2 km; (b) 9