Riordan received $5 from his father in the 1st week of school and $10 in the 2nd week. Each week, he receives $5 more than the week before.
- How much money did he received in the 17th week?
- In which week did he receive $25?
(a)
Amount that Riordan received on 1st Week = $5
Amount that Riordan received on 2nd Week = $16
Formula:
Amount received each week = 5 + (Week number - 1) x $5
Amount received on Week 17
= 5 + (17 - 1) x 5
= 5 + 16 x 5
= 5 + 80
= $85
(b)
Week number that Riordan received $25
= [(25 - 5) ÷ 5] + 1
= (20 ÷ 5) + 1
= 4 + 1
= 5
Answer(s): (a) $85; (b) 5