The difference between consecutive terms (numbers that come after each other) in arithmetic sequences is the same. That means you add the same number every time to get the next number. To figure out which choices are arithmetic sequences, just see if the differences are the same.
Choice A) 1, -2, 3, -4, 5, ... -2 - 1 = -3 3 - (-2) = 5 The difference is not constant, so it is not an arithmetic sequence.
Choice B) 12,345, 12,346, 12,347, 12,348, 12,349, ... 12,346 - 12,345 = 1 12,347 - 12,346 = 1 The difference is constant, so it is an arithmetic sequence.
Choice C) <span>154, 171, 188, 205, 222, ... 171 - 154 = 17 188 - 171 = 17 The difference is constant, so it is an arithmetic sequence.
Choice D) </span><span>1, 8, 16, 24, 32, ... 8 - 1 = 7 16 - 8 = 8 </span>The difference is not constant, so it is not an arithmetic sequence. Choice E) <span>-3, -10, -17, -24, -31, ... -10 - (-3) = -7 -17 - (-10) = -7 </span>The difference is constant, so it is an arithmetic sequence.
Work for Triangle A: 90 + 52 = 142. 180 - 142 = 38.
Work for Triangle B: Unidentifiable because there is no indicator to tell you if any of the angles/lines are equal. Generally there will be a "double lined" indicator in the corners of which a triangles angles are equal.
Work for Triangle C: Same as B.
Work for Triangle D: 90 + 20 = 110. 180 - 110 = 70.
Work for Triangle E: 90 + 50 = 140. 180 - 140 = 40.
