The table shows how much Vanessa saves daily. For each subsequent day, she saves $4 more than the previous day.
- How much will Vanessa save on Day 11?
- On which day will Vanessa save $78?
- How much savings will Vanessa 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 11
= 11 x 4 + 10
= $54
(b)
Number of days that Vanessa takes to save $78
= (78 - 10) ÷ 4
= 68 ÷ 4
= 17
(c)
Total savings that Vanessa saves by Day 17
= 14 + 18 + ... + 74 + 78
= (14 + 78) x (17 ÷ 2)
= 92 x 8.5
= $782
Answer(s): (a) $54; (b) 17; (c) $782
