Elijah received $5 from his father in the 1st week of school and $9 in the 2nd week. Each week, he receives $4 more than the week before.
- How much money did he received in the 20th week?
- In which week did he receive $21?
(a)
Amount that Elijah received on 1st Week = $5
Amount that Elijah received on 2nd Week = $19
Formula:
Amount received each week = 5 + (Week number - 1) x $4
Amount received on Week 20
= 5 + (20 - 1) x 4
= 5 + 19 x 4
= 5 + 76
= $81
(b)
Week number that Elijah received $21
= [(21 - 5) ÷ 4] + 1
= (16 ÷ 4) + 1
= 4 + 1
= 5
Answer(s): (a) $81; (b) 5