Adam saves $1 in the 1st week and $4 in the 2nd week.
Each week, he saves $3 more than the week before.
- How much money does he save in the 7th week?
- In which week does he save $52?
(a)
Amount that Adam saves on Week 1: $1
Amount that Adam saves on Week 2: $4 = 1 + 3 = 1 + (3 x 1)
Amount that Adam saves on Week 3: $7 = 1 + 3 + 3 = 1 + (3 x 2)
Amount that Adam saves on a certain week = 1 +(3 x (Week number - 1))
Amount that Adam saves on Week 7
= 1 + 3 × (7 - 1)
= 1 + 3 × 6
= 1 + 18
= $19
(b)
1 + 3 x (Week number - 1) = 52
3 x (Week number - 1) = 52 - 1
3 x (Week number - 1) = 51
Week number - 1 = 51 ÷ 3
Week number - 1 = 17
Week number = 17 + 1
Week number = 18
Answer(s): (a) $19; (b) 18