The table shows how much Rachel saves daily. For each subsequent day, she saves $8 more than the previous day.
- How much will Rachel save on Day 11?
- On which day will Rachel save $178?
- How much savings will Rachel have in total by the day found in part (b)?
(a)
Pattern for the amount saved
Day 1: 1 x 8 + 10 = $18
Day 2: 2 x 8 + 10 = $26
Day 3: 3 x 8 + 10 = $34
Day 4: 4 x 8 + 10 = $42
Formula
Amount saved = Day Number x 8 + 10
Amount saved on Day 11
= 11 x 8 + 10
= $98
(b)
Number of days that Rachel takes to save $178
= (178 - 10) ÷ 8
= 168 ÷ 8
= 21
(c)
Total savings that Rachel saves by Day 21
= 18 + 26 + ... + 170 + 178
= (18 + 178) x (21 ÷ 2)
= 196 x 10.5
= $2058
Answer(s): (a) $98; (b) 21; (c) $2058