Adam saves $4 in the 1st week and $6 in the 2nd week.
Each week, he saves $2 more than the week before.
- How much money does he save in the 10th week?
- In which week does he save $46?
(a)
Amount that Adam saves on Week 1: $4
Amount that Adam saves on Week 2: $6 = 4 + 2 = 4 + (2 x 1)
Amount that Adam saves on Week 3: $8 = 4 + 2 + 2 = 4 + (2 x 2)
Amount that Adam saves on a certain week = 4 +(2 x (Week number - 1))
Amount that Adam saves on Week 10
= 4 + 2 × (10 - 1)
= 4 + 2 × 9
= 4 + 18
= $22
(b)
4 + 2 x (Week number - 1) = 46
2 x (Week number - 4) = 46 - 4
2 x (Week number - 4) = 42
Week number - 1 = 42 ÷ 2
Week number - 1 = 21
Week number = 21 + 1
Week number = 22
Answer(s): (a) $22; (b) 22
