The table shows how much Elyse saves daily. For each subsequent day, she saves $5 more than the previous day.
- How much will Elyse save on Day 9?
- On which day will Elyse save $170?
- How much savings will Elyse have in total by the day found in part (b)?
(a)
Pattern for the amount saved
Day 1: 1 x 5 + 10 = $15
Day 2: 2 x 5 + 10 = $20
Day 3: 3 x 5 + 10 = $25
Day 4: 4 x 5 + 10 = $30
Formula
Amount saved = Day Number x 5 + 10
Amount saved on Day 9
= 9 x 5 + 10
= $55
(b)
Number of days that Elyse takes to save $170
= (170 - 10) ÷ 5
= 160 ÷ 5
= 32
(c)
Total savings that Elyse saves by Day 32
= 15 + 20 + ... + 165 + 170
= (15 + 170) x (32 ÷ 2)
= 185 x 16
= $2960
Answer(s): (a) $55; (b) 32; (c) $2960