The table shows how much Penelope saves daily. For each subsequent day, she saves $4 more than the previous day.
- How much will Penelope save on Day 8?
- On which day will Penelope save $138?
- How much savings will Penelope have in total by the day found in part (b)?
(a)
Pattern for the amount saved
Day 1: 1 x 4 + 10 = $14
Day 2: 2 x 4 + 10 = $18
Day 3: 3 x 4 + 10 = $22
Day 4: 4 x 4 + 10 = $26
Formula
Amount saved = Day Number x 4 + 10
Amount saved on Day 8
= 8 x 4 + 10
= $42
(b)
Number of days that Penelope takes to save $138
= (138 - 10) ÷ 4
= 128 ÷ 4
= 32
(c)
Total savings that Penelope saves by Day 32
= 14 + 18 + ... + 134 + 138
= (14 + 138) x (32 ÷ 2)
= 152 x 16
= $2432
Answer(s): (a) $42; (b) 32; (c) $2432