The table shows how much Tina saves daily. For each subsequent day, she saves $10 more than the previous day.
- How much will Tina save on Day 12?
- On which day will Tina save $70?
- How much savings will Tina 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 12
= 12 x 10 + 10
= $130
(b)
Number of days that Tina takes to save $70
= (70 - 10) ÷ 10
= 60 ÷ 10
= 6
(c)
Total savings that Tina saves by Day 6
= 20 + 30 + ... + 60 + 70
= (20 + 70) x (6 ÷ 2)
= 90 x 3
= $270
Answer(s): (a) $130; (b) 6; (c) $270