The table shows how much Opal saves daily. For each subsequent day, she saves $4 more than the previous day.
- How much will Opal save on Day 7?
- On which day will Opal save $142?
- How much savings will Opal have in total by the day found in part (b)?
(a)
Pattern for the amount saved
Day 1: 1 x 4 + 10 = $14
Day 2: 2 x 4 + 10 = $18
Day 3: 3 x 4 + 10 = $22
Day 4: 4 x 4 + 10 = $26
Formula
Amount saved = Day Number x 4 + 10
Amount saved on Day 7
= 7 x 4 + 10
= $38
(b)
Number of days that Opal takes to save $142
= (142 - 10) ÷ 4
= 132 ÷ 4
= 33
(c)
Total savings that Opal saves by Day 33
= 14 + 18 + ... + 138 + 142
= (14 + 142) x (33 ÷ 2)
= 156 x 16.5
= $2574
Answer(s): (a) $38; (b) 33; (c) $2574