Chapter test: Letter Series

Explanation: Opposite letters add up to 27. E is 5, so the opposite is 27 − 5 = 22, which is V. The letters U at 21 and W at 23 are the plus or minus one distractors.

Explanation: The positions are 1, 3, 6, 10, 15 and the gaps are 2, 3, 4, 5, so the next gap is 6 and the answer is 15 + 6 = 21, which is U. Reusing the gap of 5 gives T, the built-in trap.

Explanation: The repeating block is aabb, written three times. Splitting the string into blocks of four gives a _ b b, a _ b b and a a _ b, so the blanks must be a, a and b. Any other set breaks the blocks, for example aba makes the second block abbb.

Explanation: The positions are 26, 23, 20, 17, 14, falling by 3 each time, so the next is 14 − 3 = 11, which is K. A gap of 2 gives L and a gap of 4 gives J, which are the two distractors.

Explanation: BDF is 2, 4, 6, MOQ is 13, 15, 17 and GIK is 7, 9, 11, all with gaps of +2 twice. RTW is 18, 20, 23, with gaps of +2 and +3, so it breaks the pattern. The matching group would have been RTV.

Explanation: This is an alternate series. Odd positions run B, D, F, H rising by 2, and even positions run Y, W, U falling by 2. The blank is the eighth term, an even position, so the answer is 21 − 2 = 19, which is S.

Explanation: These are opposite-letter pairs whose positions add up to 27. The first letters run A, B, C, D, E and the opposite of E is 27 − 5 = 22, which is V, so the answer is EV. In EU the sum is only 26, EW leaves the second letter unchanged and FV moves the first letter too far.

Explanation: Inside each group the gap is +2 and between groups each letter moves +1. The next group therefore starts at D and runs D, F, H. In DFG and DEH the internal gap of +2 is broken, and EGI skips a whole group.

Explanation: Using the EJOTY anchor T = 20, R is two before T, so R = 18. The value 17 is Q and 19 is S. The value 9 is the position of R from the right, since 27 − 18 = 9, so it is a direction trap.

Explanation: Position from the left is 27 minus the position from the right, so 27 − 7 = 20, which is T. Subtracting from 26 instead gives 19, that is S, the standard error. U is 6th from the right and G is 7th from the left.