The table shows how much Sabrina saves daily. For each subsequent day, she saves $9 more than the previous day.
- How much will Sabrina save on Day 11?
- On which day will Sabrina save $163?
- How much savings will Sabrina 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 11
= 11 x 9 + 10
= $109
(b)
Number of days that Sabrina takes to save $163
= (163 - 10) ÷ 9
= 153 ÷ 9
= 17
(c)
Total savings that Sabrina saves by Day 17
= 19 + 28 + ... + 154 + 163
= (19 + 163) x (17 ÷ 2)
= 182 x 8.5
= $1547
Answer(s): (a) $109; (b) 17; (c) $1547
