Clerical questions test whether you can compare, count and order exactly, at speed. They come in five kinds: matching a code to a reference, counting pairs of codes that are exactly alike, checking a copy against its original, putting names in alphabetic order, and counting a pattern in a long string of digits. None of them is hard to understand, and every one can be settled for certain by checking. A miss is a slip: a skipped character, a lost place, a count that drifted by one. The first chapter gives a checking routine that works on all five kinds, and the rest give the fastest reliable method for each.
Each chapter opens with the short version. Tap one to read the detail.
A routine that does not slip
~2 min
Every clerical item can be settled for certain by checking, so a miss is a slip rather than a gap in knowledge. Read codes in short groups, keep your place, check to the last character, and work out your answer before you look at the choices.
Speed comes from repeating one reliable routine, not from rushing. Pick a way of checking each kind of item and use it every time. When your misses climb, drop back to the last pace at which you were accurate.
Read a long code in groups of three or four characters. 4HV82NBT7 becomes 4HV, 82N and BT7, and comparing three characters at a time is far easier than holding nine. Grouping also tells you which group holds a difference, so you can look at that group alone. Keep your place with a fingertip or the cursor on each code, and move both together, because an eye that lands one character off can make two different codes look alike.
The trap is calling a match because the start agreed. A changed character can sit anywhere, the last position included, so every comparison runs to the final character. The reverse also holds: once you find one difference, the two codes are different and you can move on. The exception is a question about what kind of error a copy contains, covered in its own chapter.
Finish your own answer before you read the options. The choices on a counting question are neighboring numbers, so a count that is off by one still lands on a choice and gives no warning. If your answer is not among the options, recount rather than taking the nearest one.
Rule: settle each item with your own complete check, then find your answer among the choices.
Matching a code to its reference
~2 min
Find the positions where the choices disagree with one another and check only those against the reference. Then read the surviving choice in full, first character to last, before you pick it.
Each wrong choice differs from the reference in a single character, so most positions tell you nothing, because every choice agrees there. Suppose the reference is KR52TX9H and the choices are KR52FX9H, KR53TX9H, KB52TX9H and KR52TX9H. The choices disagree only at the second, fourth and fifth positions. Check those three against the reference, where they read R, 2 and T, and only the last choice survives.
When the codes are long, work column by column. Take the first group of the reference, compare it across all four choices, and drop any choice that fails. Then move to the next group. You hold one short group in mind at a time.
The trap is trusting elimination alone. A slip can cross out the right answer and leave a wrong one standing, so read the last survivor against the reference once more, start to finish. If it fails, one of your earlier eliminations was a mistake. Include the first and last characters in every check, since they are as likely to be changed as any other.
A changed character stays the same kind: a digit becomes another digit, and a letter becomes another letter. The confusions to guard against are within a kind, such as 3 and 8, 1 and 7, 6 and 9, B and D, M and N, or V and W. Naming each character to yourself forces you to decide what it is instead of accepting a shape that only looks right.
Rule: narrow the check to the positions where the choices differ, then confirm the survivor in full.
Counting pairs that are exactly alike
~2 min
Count the pairs first, mark a verdict beside each one, and call a pair alike only after checking it to the last character. The answer can be zero, and it can be every pair.
Before you compare anything, count the pairs. The total lets you check your tally at the end, because the alike and different pairs must add up to it.
Compare across the gap in chunks: the first three characters on the left, then the first three on the right, then the next three on each side. Mark each verdict with a tick or a cross before you read the next line, and count the marks only at the end. A running total kept in your head while you compare is where tallies slip.
Take five pairs: 7DW3KH and 7DW3KH, PL94NZ and PL94MZ, 28GTX5 and 28GTX5, HJ6RB1 and HJ6RB7, SC3KD8 and SC3KD8. The second pair differs at its fifth character, N against M, and the fourth at its last, 1 against 7. Two pairs differ, so three are alike. One mismatch settles a pair as different, while alike needs a full check, so counting the different pairs and subtracting can be the faster route. If you do, finish the subtraction: the question asks for the alike pairs, so the different count is not your answer.
The trap is reading "exactly" loosely: a pair that agrees in five characters out of six is still different. Do not expect a mix, either; if every pair checks out, the answer is the total, and if none does, it is zero.
Rule: count the total, mark a verdict for each pair, and call a pair alike only after a full check.
Checking a copy against its original
~2 min
Compare the lengths first, then the characters. A replaced character changes one position, two swapped neighbors trade places, and a dropped character shifts everything after it, so the pattern of mismatches names the error.
Start with the length, the quickest test. Take the original BX37LP. A copy with five characters has lost one before you compare anything, while a copy with six leaves a replaced character, two swapped neighbors, or an exact match.
Each kind of error leaves its own pattern. BX37LD differs only in the last position, so one character was replaced. BX73LP holds the same characters in a different order: the 3 and the 7 traded places, so the two wrong positions hold each other's character. BX7LP is one character short, and from the third position on every character looks wrong, because each one slid one place to the left after the 3 was dropped. A run of mismatches that starts at one point and continues to the end is the mark of a missing character.
The trap is stopping at the first difference. That works when the question only asks whether two codes match, but when the options name the error, the first wrong position does not tell you which kind it is. Check the next character too. If it is also wrong and the two positions hold each other's characters, the error is a swap, not a replacement.
A single replaced character with the length unchanged fits the option for a plain error, not the missing or swapped one. When you find no difference, choose the match only after checking every character, since a copy that looks right at a glance is the easiest place to stop early.
Rule: check the length, then the characters, and name the error by its pattern of mismatches.
Putting names in alphabetic order
~2 min
File by surname, comparing one letter at a time until a letter differs, and let a name that runs out first file first. Use the given name only when surnames match, then count to the position the question asks for.
The names in these items are written surname first, with a comma, the way an index lists people. The surname is the filing key: Ostrander, Wes files before Pemberton, Ada because O comes before P, even though A comes before W.
Compare two surnames letter by letter from the left and stop at the first letter that differs. Pemberton and Pembroke agree in P, E, M and B, then have E against R, so Pemberton files first. When one name is the start of another, the shorter one files first: Pell comes before Pellegrino, because a name that has ended comes before any letter. When surnames match exactly, run the same test on the given names. Ashdown, Tobias and Ashdown, Toby agree in T, O and B, then have I against Y, so Tobias files first.
Each item lists four names. To work quickly, sort by first letter and look closely only where initials repeat. For first or last you need only the earliest or latest name; for second, take the later of the two earliest names, and for third, the earlier of the two latest.
The trap is answering with whatever name sits in the asked position of the printed list. The list is in mixed order, so write your sorted order down, even as four initials, and count from there. Names one vowel apart, such as Corwen and Corwin, also deserve a slow, letter-by-letter look.
Rule: compare letter by letter, let the shorter name win a tie, and count positions in your own sorted list.
Counting a pattern in a string of digits
~2 min
Anchor on the pattern's last digit, look back to test each condition, and mark every confirmed hit. Check the spots that cross your group edges, and treat zero as a real answer.
A pattern question asks how often something occurs, such as a 2 directly after a 7, where the digit before the 7 is odd. Find every 2 and look back from each one. Anchor on a named digit rather than a condition: a named digit is one of ten, while odd fits five, so the digit leaves fewer spots to check.
In 381729547216970723 there are three 2s, and each has a 7 just before it. Before those 7s come 1, 4 and 0. Only the 1 is odd, so the count is 1. Know parity by heart: the odd digits are 1, 3, 5, 7 and 9. Zero is even, because it divides by 2 with nothing left over, so the 0 fails the odd condition.
Groups of four keep your place in a long string, but a pattern can start in one group and end in the next. Split the example as 3817 2954 7216 9707 23, and each of its three odd-7-2 runs crosses a group edge, so a search inside each group finds none. After each group, read its last two digits with the start of the next.
The trap is counting a near miss: a 7 followed by a 2 is not a hit when the digit before the 7 is even. A string can hold all the right digits without ever lining them up, and then the correct count is zero. Mark each confirmed hit as you find it and count the marks at the end.
Rule: anchor on the last digit, test every condition, and trust a count of zero.
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