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 5th week?
- In which week does he save $37?
(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 5
= 1 + 3 × (5 - 1)
= 1 + 3 × 4
= 1 + 12
= $13
(b)
1 + 3 x (Week number - 1) = 37
3 x (Week number - 1) = 37 - 1
3 x (Week number - 1) = 36
Week number - 1 = 36 ÷ 3
Week number - 1 = 12
Week number = 12 + 1
Week number = 13
Answer(s): (a) $13; (b) 13