Ethan saved $3 in the first week and increased his savings by $5 each week. How much would he have saved at the end of 9 weeks?
Make a list: 3, 8, 13, 18, 23, 28, 33, 38, 43
Using rainbow method: 3 + 43 = 468 + 38 = 4613 + 33 = 4618 + 28 = 46Sum of each pair = 46Number of pairs: 4, left: 23 Sum of all pairs = [46 x 4] + 23 = 184 + 23 = $207 Answer(s): $207