Charlie saved $3 in the first week and increased his savings by $6 each week. How much would he have saved at the end of 9 weeks?
Make a list: 3, 9, 15, 21, 27, 33, 39, 45, 51
Using rainbow method: 3 + 51 = 549 + 45 = 5415 + 39 = 5421 + 33 = 54Sum of each pair = 54Number of pairs: 4, left: 27 Sum of all pairs = [54 x 4] + 27 = 216 + 27 = $243 Answer(s): $243