The table shows how much Eva saves daily. For each subsequent day, she saves $10 more than the previous day.
- How much will Eva save on Day 9?
- On which day will Eva save $130?
- How much savings will Eva have in total by the day found in part (b)?
(a)
Pattern for the amount saved
Day 1: 1 x 10 + 10 = $20
Day 2: 2 x 10 + 10 = $30
Day 3: 3 x 10 + 10 = $40
Day 4: 4 x 10 + 10 = $50
Formula
Amount saved = Day Number x 10 + 10
Amount saved on Day 9
= 9 x 10 + 10
= $100
(b)
Number of days that Eva takes to save $130
= (130 - 10) ÷ 10
= 120 ÷ 10
= 12
(c)
Total savings that Eva saves by Day 12
= 20 + 30 + ... + 120 + 130
= (20 + 130) x (12 ÷ 2)
= 150 x 6
= $900
Answer(s): (a) $100; (b) 12; (c) $900