Adam saves $4 in the 1st week and $9 in the 2nd week.
Each week, he saves $5 more than the week before.
- How much money does he save in the 6th week?
- In which week does he save $29?
(a)
Amount that Adam saves on Week 1: $4
Amount that Adam saves on Week 2: $9 = 4 + 5 = 4 + (5 x 1)
Amount that Adam saves on Week 3: $14 = 4 + 5 + 5 = 4 + (5 x 2)
Amount that Adam saves on a certain week = 4 +(5 x (Week number - 1))
Amount that Adam saves on Week 6
= 4 + 5 × (6 - 1)
= 4 + 5 × 5
= 4 + 25
= $29
(b)
4 + 5 x (Week number - 1) = 29
5 x (Week number - 4) = 29 - 4
5 x (Week number - 4) = 25
Week number - 1 = 25 ÷ 5
Week number - 1 = 5
Week number = 5 + 1
Week number = 6
Answer(s): (a) $29; (b) 6
