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 11?
- On which day will Gillian save $148?
- 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 11
= 11 x 3 + 10
= $43
(b)
Number of days that Gillian takes to save $148
= (148 - 10) ÷ 3
= 138 ÷ 3
= 46
(c)
Total savings that Gillian saves by Day 46
= 13 + 16 + ... + 145 + 148
= (13 + 148) x (46 ÷ 2)
= 161 x 23
= $3703
Answer(s): (a) $43; (b) 46; (c) $3703
