The table shows how much Gillian saves daily. For each subsequent day, she saves $3 more than the previous day.
- How much will Gillian save on Day 5?
- On which day will Gillian save $160?
- How much savings will Gillian have in total by the day found in part (b)?
(a)
Pattern for the amount saved
Day 1: 1 x 3 + 10 = $13
Day 2: 2 x 3 + 10 = $16
Day 3: 3 x 3 + 10 = $19
Day 4: 4 x 3 + 10 = $22
Formula
Amount saved = Day Number x 3 + 10
Amount saved on Day 5
= 5 x 3 + 10
= $25
(b)
Number of days that Gillian takes to save $160
= (160 - 10) ÷ 3
= 150 ÷ 3
= 50
(c)
Total savings that Gillian saves by Day 50
= 13 + 16 + ... + 157 + 160
= (13 + 160) x (50 ÷ 2)
= 173 x 25
= $4325
Answer(s): (a) $25; (b) 50; (c) $4325