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 10th week?
- In which week does he save $37?
(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 10
= 1 + 6 × (10 - 1)
= 1 + 6 × 9
= 1 + 54
= $55
(b)
1 + 6 x (Week number - 1) = 37
6 x (Week number - 1) = 37 - 1
6 x (Week number - 1) = 36
Week number - 1 = 36 ÷ 6
Week number - 1 = 6
Week number = 6 + 1
Week number = 7
Answer(s): (a) $55; (b) 7