The table shows how much Wendy saves daily. For each subsequent day, she saves $10 more than the previous day.
- How much will Wendy save on Day 12?
- On which day will Wendy save $120?
- How much savings will Wendy 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 Wendy takes to save $120
= (120 - 10) ÷ 10
= 110 ÷ 10
= 11
(c)
Total savings that Wendy saves by Day 11
= 20 + 30 + ... + 110 + 120
= (20 + 120) x (11 ÷ 2)
= 140 x 5.5
= $770
Answer(s): (a) $130; (b) 11; (c) $770
