The table shows how much Esther saves daily. For each subsequent day, she saves $11 more than the previous day.
- How much will Esther save on Day 5?
- On which day will Esther save $87?
- How much savings will Esther have in total by the day found in part (b)?
(a)
Pattern for the amount saved
Day 1: 1 x 11 + 10 = $21
Day 2: 2 x 11 + 10 = $32
Day 3: 3 x 11 + 10 = $43
Day 4: 4 x 11 + 10 = $54
Formula
Amount saved = Day Number x 11 + 10
Amount saved on Day 5
= 5 x 11 + 10
= $65
(b)
Number of days that Esther takes to save $87
= (87 - 10) ÷ 11
= 77 ÷ 11
= 7
(c)
Total savings that Esther saves by Day 7
= 21 + 32 + ... + 76 + 87
= (21 + 87) x (7 ÷ 2)
= 108 x 3.5
= $378
Answer(s): (a) $65; (b) 7; (c) $378
