Adam saves $1 in the 1st week and $7 in the 2nd week.
Each week, he saves $6 more than the week before.
- How much money does he save in the 4th week?
- In which week does he save $31?
(a)
Amount that Adam saves on Week 1: $1
Amount that Adam saves on Week 2: $7 = 1 + 6 = 1 + (6 x 1)
Amount that Adam saves on Week 3: $13 = 1 + 6 + 6 = 1 + (6 x 2)
Amount that Adam saves on a certain week = 1 +(6 x (Week number - 1))
Amount that Adam saves on Week 4
= 1 + 6 × (4 - 1)
= 1 + 6 × 3
= 1 + 18
= $19
(b)
1 + 6 x (Week number - 1) = 31
6 x (Week number - 1) = 31 - 1
6 x (Week number - 1) = 30
Week number - 1 = 30 ÷ 6
Week number - 1 = 5
Week number = 5 + 1
Week number = 6
Answer(s): (a) $19; (b) 6