The table shows how much Usha saves daily. For each subsequent day, she saves $8 more than the previous day.
- How much will Usha save on Day 10?
- On which day will Usha save $98?
- How much savings will Usha have in total by the day found in part (b)?
(a)
Pattern for the amount saved
Day 1: 1 x 8 + 10 = $18
Day 2: 2 x 8 + 10 = $26
Day 3: 3 x 8 + 10 = $34
Day 4: 4 x 8 + 10 = $42
Formula
Amount saved = Day Number x 8 + 10
Amount saved on Day 10
= 10 x 8 + 10
= $90
(b)
Number of days that Usha takes to save $98
= (98 - 10) ÷ 8
= 88 ÷ 8
= 11
(c)
Total savings that Usha saves by Day 11
= 18 + 26 + ... + 90 + 98
= (18 + 98) x (11 ÷ 2)
= 116 x 5.5
= $638
Answer(s): (a) $90; (b) 11; (c) $638