Adam saves $2 in the 1st week and $7 in the 2nd week.
Each week, he saves $5 more than the week before.
- How much money does he save in the 6th week?
- In which week does he save $17?
(a)
Amount that Adam saves on Week 1: $2
Amount that Adam saves on Week 2: $7 = 2 + 5 = 2 + (5 x 1)
Amount that Adam saves on Week 3: $12 = 2 + 5 + 5 = 2 + (5 x 2)
Amount that Adam saves on a certain week = 2 +(5 x (Week number - 1))
Amount that Adam saves on Week 6
= 2 + 5 × (6 - 1)
= 2 + 5 × 5
= 2 + 25
= $27
(b)
2 + 5 x (Week number - 1) = 17
5 x (Week number - 2) = 17 - 2
5 x (Week number - 2) = 15
Week number - 1 = 15 ÷ 5
Week number - 1 = 3
Week number = 3 + 1
Week number = 4
Answer(s): (a) $27; (b) 4