Adam saves $1 in the 1st week and $3 in the 2nd week.
Each week, he saves $2 more than the week before.
- How much money does he save in the 5th week?
- In which week does he save $41?
(a)
Amount that Adam saves on Week 1: $1
Amount that Adam saves on Week 2: $3 = 1 + 2 = 1 + (2 x 1)
Amount that Adam saves on Week 3: $5 = 1 + 2 + 2 = 1 + (2 x 2)
Amount that Adam saves on a certain week = 1 +(2 x (Week number - 1))
Amount that Adam saves on Week 5
= 1 + 2 × (5 - 1)
= 1 + 2 × 4
= 1 + 8
= $9
(b)
1 + 2 x (Week number - 1) = 41
2 x (Week number - 1) = 41 - 1
2 x (Week number - 1) = 40
Week number - 1 = 40 ÷ 2
Week number - 1 = 20
Week number = 20 + 1
Week number = 21
Answer(s): (a) $9; (b) 21