Adam saves $2 in the 1st week and $7 in the 2nd week.
Each week, he saves $5 more than the week before.
- How much money does he save in the 5th week?
- In which week does he save $47?
(a)
Amount that Adam saves on Week 1: $2
Amount that Adam saves on Week 2: $7 = 2 + 5 = 2 + (5 x 1)
Amount that Adam saves on Week 3: $12 = 2 + 5 + 5 = 2 + (5 x 2)
Amount that Adam saves on a certain week = 2 +(5 x (Week number - 1))
Amount that Adam saves on Week 5
= 2 + 5 × (5 - 1)
= 2 + 5 × 4
= 2 + 20
= $22
(b)
2 + 5 x (Week number - 1) = 47
5 x (Week number - 2) = 47 - 2
5 x (Week number - 2) = 45
Week number - 1 = 45 ÷ 5
Week number - 1 = 9
Week number = 9 + 1
Week number = 10
Answer(s): (a) $22; (b) 10