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SEAMO 2027 - Paper B - SET 08 - Self-study

Question 1

SEAMO self-study edition 2027; not an official 2027 paper. Original source years are retained. 25 questions, 90 minutes; Q1–10: 3 points, Q11–20: 4 points, Q21–25: 6 points, total 100. Original response types and all subparts are preserved. Verified is an editorial convention; source defects, necessary assumptions and unresolved mathematical uncertainty are disclosed.

Evaluate $1+2-3+4+5-6+\cdots+97+98-99+100$.
  1. 1650
  2. 1632
  3. 1684
  4. 1691
  5. 1732

Question 2

How many squares are there in the $4\times4$ grid?

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  1. 28
  2. 30
  3. 32
  4. 34
  5. 36

Question 3

The side length of a square is increased by 50%. By what percentage does its area increase?
  1. 80%
  2. 90%
  3. 100%
  4. 125%
  5. 150%

Question 4

In the figure, the shaded area is $60\text{ cm}^2$. E is the midpoint of BC, and F is the intersection of AE and BD. Find the area of square ABCD in square centimetres.

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Question 5

The numbers 1 through 8 are placed in the circles, each used once, so that every drawn straight line containing three circles has the same sum. Find x.

Use each integer from 1 through 8 exactly once. Only the four straight lines that contain three circles must have equal sums.

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Question 6

Find the smallest value of k such that $k+2^{23}$ is divisible by 31.

For self-study, take k to be a nonnegative integer. The printed question does not specify its domain.

Question 7

Ali takes $\frac13$ of the stones from a bag. Bala then takes $\frac13$ of the remaining stones, and Chakor takes $\frac13$ of what then remains. There are 32 stones left. How many stones were in the bag at first?

Question 8

If Ms. Woodley gives 5 sweets to each student, she has 32 sweets left. If she gives each student 8 sweets, five students receive none. How many sweets does she have?

In the second distribution, all sweets are used: every student except the five receives exactly 8 sweets.
  1. 140
  2. 144
  3. 148
  4. 152
  5. None of the above

Question 9

Sam has 63 banknotes, each worth either 2 dollars or 5 dollars. Their total value is 171 dollars. How many 5-dollar notes does he have?
  1. 15
  2. 16
  3. 17
  4. 18
  5. None of the above

Question 10

Whole numbers starting from 0 are arranged in the array shown. In which row is 2019? Enter the row number.

Continue the displayed L-shaped layering of consecutive whole numbers. “Row” is counted downwards from Row 1.

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Question 11

ABCD is a square and EFGH is a rectangle. The figure gives $FB=2AF$, $BG=2GC$, $DH=2HC$ and $DE=2AE$. Given $FB=4\text{ cm}$, find the area of EFGH in square centimetres.

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  1. 12
  2. 13
  3. 14
  4. 16
  5. None of the above

Question 12

What is the 100th number in the sequence $1,4,7,10,\ldots$?

Continue the constant increase shown by the sequence.
  1. 292
  2. 294
  3. 296
  4. 298
  5. 300

Question 13

How many rectangles are there in the figure?

Question illustration
  1. 22
  2. 24
  3. 25
  4. 26
  5. 27

Question 14

Given $6\bullet5=6+5-4+3-2=8$ and $7\bullet3=7+6-5=8$, find $10\bullet6$.

For this self-study item, a bullet b means: write b consecutive descending terms starting at a, put plus between the first two terms, and then alternate minus and plus. This is the intended continuation suggested by the examples, not a uniquely determined definition from two examples alone.
  1. 13
  2. 14
  3. 15
  4. 16
  5. 17

Question 15

What is the first number in the 10th row of the array shown?

Continue the consecutive positive odd numbers, with row lengths 1, 3, 5, 7, … as displayed.

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  1. 163
  2. 165
  3. 167
  4. 169
  5. 171

Question 16

Shawn and Matthew have 76 books altogether. Shawn has three times as many books as Matthew. How many books does Shawn have?
  1. 19
  2. 27
  3. 47
  4. 57
  5. None of the above

Question 17

A fruit seller packs oranges into bags. If he puts 5 oranges in each bag, 14 oranges remain. The source then says: “If he packs 7 oranges into each bag, he will need another 2 bags.” How many oranges does he have?

Source correction for self-study: replace “need another 2 bags” by “have 2 bags left unused”, with all used bags full. Answer the corrected version; the literal printed wording is inconsistent with the options.
  1. 76
  2. 78
  3. 80
  4. 82
  5. 84

Question 18

Place the numbers 1 through 9, each once, in the circles. The sum along each of the two straight lines is S. The centre already contains 5. Find S.

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  1. 25
  2. 26
  3. 22
  4. 34
  5. None of the above

Question 19

Find A in the number puzzle shown.

Use the same simple arithmetic relationship among the four corners in all three boxes, as intended by this pattern puzzle. The source does not define a rule, so other artificial rules are possible.

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  1. 35
  2. 36
  3. 38
  4. 40
  5. 42

Question 20

Alan, Ben and Chad run a 100-metre race. When Alan finishes, Ben is 10 m behind him. When Ben finishes, Chad is 10 m behind him. How far is Chad from the finish when Alan finishes? Give metres.

Assume the runners start together from the same line and each runs at a constant speed.