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 8th week?
- In which week does he save $51?
(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 8
= 1 + 5 × (8 - 1)
= 1 + 5 × 7
= 1 + 35
= $36
(b)
1 + 5 x (Week number - 1) = 51
5 x (Week number - 1) = 51 - 1
5 x (Week number - 1) = 50
Week number - 1 = 50 ÷ 5
Week number - 1 = 10
Week number = 10 + 1
Week number = 11
Answer(s): (a) $36; (b) 11