The table shows how much Jade saves daily. For each subsequent day, she saves $5 more than the previous day.
- How much will Jade save on Day 9?
- On which day will Jade save $120?
- How much savings will Jade 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 Jade takes to save $120
= (120 - 10) ÷ 5
= 110 ÷ 5
= 22
(c)
Total savings that Jade saves by Day 22
= 15 + 20 + ... + 115 + 120
= (15 + 120) x (22 ÷ 2)
= 135 x 11
= $1485
Answer(s): (a) $55; (b) 22; (c) $1485