Adam saves $2 in the 1st week and $4 in the 2nd week.
Each week, he saves $2 more than the week before.
- How much money does he save in the 8th week?
- In which week does he save $30?
(a)
Amount that Adam saves on Week 1: $2
Amount that Adam saves on Week 2: $4 = 2 + 2 = 2 + (2 x 1)
Amount that Adam saves on Week 3: $6 = 2 + 2 + 2 = 2 + (2 x 2)
Amount that Adam saves on a certain week = 2 +(2 x (Week number - 1))
Amount that Adam saves on Week 8
= 2 + 2 × (8 - 1)
= 2 + 2 × 7
= 2 + 14
= $16
(b)
2 + 2 x (Week number - 1) = 30
2 x (Week number - 2) = 30 - 2
2 x (Week number - 2) = 28
Week number - 1 = 28 ÷ 2
Week number - 1 = 14
Week number = 14 + 1
Week number = 15
Answer(s): (a) $16; (b) 15