Adam saves $4 in the 1st week and $10 in the 2nd week.
Each week, he saves $6 more than the week before.
- How much money does he save in the 9th week?
- In which week does he save $34?
(a)
Amount that Adam saves on Week 1: $4
Amount that Adam saves on Week 2: $10 = 4 + 6 = 4 + (6 x 1)
Amount that Adam saves on Week 3: $16 = 4 + 6 + 6 = 4 + (6 x 2)
Amount that Adam saves on a certain week = 4 +(6 x (Week number - 1))
Amount that Adam saves on Week 9
= 4 + 6 × (9 - 1)
= 4 + 6 × 8
= 4 + 48
= $52
(b)
4 + 6 x (Week number - 1) = 34
6 x (Week number - 4) = 34 - 4
6 x (Week number - 4) = 30
Week number - 1 = 30 ÷ 6
Week number - 1 = 5
Week number = 5 + 1
Week number = 6
Answer(s): (a) $52; (b) 6