Adam saves $5 in the 1st week and $8 in the 2nd week.
Each week, he saves $3 more than the week before.
- How much money does he save in the 10th week?
- In which week does he save $29?
(a)
Amount that Adam saves on Week 1: $5
Amount that Adam saves on Week 2: $8 = 5 + 3 = 5 + (3 x 1)
Amount that Adam saves on Week 3: $11 = 5 + 3 + 3 = 5 + (3 x 2)
Amount that Adam saves on a certain week = 5 +(3 x (Week number - 1))
Amount that Adam saves on Week 10
= 5 + 3 × (10 - 1)
= 5 + 3 × 9
= 5 + 27
= $32
(b)
5 + 3 x (Week number - 1) = 29
3 x (Week number - 5) = 29 - 5
3 x (Week number - 5) = 24
Week number - 1 = 24 ÷ 3
Week number - 1 = 8
Week number = 8 + 1
Week number = 9
Answer(s): (a) $32; (b) 9
