The table shows how much Xylia saves daily. For each subsequent day, she saves $7 more than the previous day.
- How much will Xylia save on Day 11?
- On which day will Xylia save $157?
- How much savings will Xylia have in total by the day found in part (b)?
(a)
Pattern for the amount saved
Day 1: 1 x 7 + 10 = $17
Day 2: 2 x 7 + 10 = $24
Day 3: 3 x 7 + 10 = $31
Day 4: 4 x 7 + 10 = $38
Formula
Amount saved = Day Number x 7 + 10
Amount saved on Day 11
= 11 x 7 + 10
= $87
(b)
Number of days that Xylia takes to save $157
= (157 - 10) ÷ 7
= 147 ÷ 7
= 21
(c)
Total savings that Xylia saves by Day 21
= 17 + 24 + ... + 150 + 157
= (17 + 157) x (21 ÷ 2)
= 174 x 10.5
= $1827
Answer(s): (a) $87; (b) 21; (c) $1827
