Adam saves $1 in the 1st week and $6 in the 2nd week.
Each week, he saves $5 more than the week before.
- How much money does he save in the 7th week?
- In which week does he save $16?
(a)
Amount that Adam saves on Week 1: $1
Amount that Adam saves on Week 2: $6 = 1 + 5 = 1 + (5 x 1)
Amount that Adam saves on Week 3: $11 = 1 + 5 + 5 = 1 + (5 x 2)
Amount that Adam saves on a certain week = 1 +(5 x (Week number - 1))
Amount that Adam saves on Week 7
= 1 + 5 × (7 - 1)
= 1 + 5 × 6
= 1 + 30
= $31
(b)
1 + 5 x (Week number - 1) = 16
5 x (Week number - 1) = 16 - 1
5 x (Week number - 1) = 15
Week number - 1 = 15 ÷ 5
Week number - 1 = 3
Week number = 3 + 1
Week number = 4
Answer(s): (a) $31; (b) 4