Adam saves $5 in the 1st week and $9 in the 2nd week.
Each week, he saves $4 more than the week before.
- How much money does he save in the 6th week?
- In which week does he save $37?
(a)
Amount that Adam saves on Week 1: $5
Amount that Adam saves on Week 2: $9 = 5 + 4 = 5 + (4 x 1)
Amount that Adam saves on Week 3: $13 = 5 + 4 + 4 = 5 + (4 x 2)
Amount that Adam saves on a certain week = 5 +(4 x (Week number - 1))
Amount that Adam saves on Week 6
= 5 + 4 × (6 - 1)
= 5 + 4 × 5
= 5 + 20
= $25
(b)
5 + 4 x (Week number - 1) = 37
4 x (Week number - 5) = 37 - 5
4 x (Week number - 5) = 32
Week number - 1 = 32 ÷ 4
Week number - 1 = 8
Week number = 8 + 1
Week number = 9
Answer(s): (a) $25; (b) 9