The table shows how much Cindy saves daily. For each subsequent day, she saves $9 more than the previous day.
- How much will Cindy save on Day 6?
- On which day will Cindy save $73?
- How much savings will Cindy 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 6
= 6 x 9 + 10
= $64
(b)
Number of days that Cindy takes to save $73
= (73 - 10) ÷ 9
= 63 ÷ 9
= 7
(c)
Total savings that Cindy saves by Day 7
= 19 + 28 + ... + 64 + 73
= (19 + 73) x (7 ÷ 2)
= 92 x 3.5
= $322
Answer(s): (a) $64; (b) 7; (c) $322