The table shows how much Kylie saves daily. For each subsequent day, she saves $9 more than the previous day.
- How much will Kylie save on Day 9?
- On which day will Kylie save $127?
- How much savings will Kylie have in total by the day found in part (b)?
(a)
Pattern for the amount saved
Day 1: 1 x 9 + 10 = $19
Day 2: 2 x 9 + 10 = $28
Day 3: 3 x 9 + 10 = $37
Day 4: 4 x 9 + 10 = $46
Formula
Amount saved = Day Number x 9 + 10
Amount saved on Day 9
= 9 x 9 + 10
= $91
(b)
Number of days that Kylie takes to save $127
= (127 - 10) ÷ 9
= 117 ÷ 9
= 13
(c)
Total savings that Kylie saves by Day 13
= 19 + 28 + ... + 118 + 127
= (19 + 127) x (13 ÷ 2)
= 146 x 6.5
= $949
Answer(s): (a) $91; (b) 13; (c) $949