Illustrative Example 1 Suppose the auditorium of the Tagaytay International Convention Center TICC) has 20 seats in the first row and that each row has 2 more seats than the previous row. If there are 30 rows in the auditorium, how many seats are in the last row? To solve real-life problems involving sequences, remember the words "SEE, PLAN, DO and LOOK BACK" Solution: SEE - What kind of sequence is involve in the problem? 20 + 22 + 24 + 26 +.. 1 PLAN - What is the appropriate formula to be used and the needed values? an = a +in-1]d Where ai = 20: d = 2: n = 30 DO - Perform the indicated operation and simplify. aitin - 1)d + 20+(30 - 1)2 + 20+(29)2 20+58 78 LOOK BACK - The answer should satisfy all the given information in the prob- lemn 20 * 22 + 24 - 26 + 28 * 30 * 32 + 34 36 + 38 40 42 +44 +46 48 50 52 54 + 56+ 58 + 60 +62 +64 + 66 + 68 + 70 * 72-74 76 + 78​