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SEAMO 2026 Paper B — Organizer self-practice SET 5

Question 1

$\overline{ab}$ is a 2-digit number such that $a=b+1$. Given that $\overline{ab}+\overline{ba}=77$, find $\overline{ab}$.
  1. 16
  2. 25
  3. 43
  4. 57
  5. None of the above

Question 2

Given $6\bullet5=6+5-4+3-2=8$ and $7\bullet3=7+6-5=8$, find $10\bullet6$.
  1. 13
  2. 14
  3. 15
  4. 16
  5. 17

Question 3

In the figure below, the perimeter of Figure A is 12 cm. Find the perimeter of Figure B.

Question illustration
  1. 17
  2. 18
  3. 19
  4. 20
  5. 21

Question 4

Shawn jogged around a park at a speed of 120 m/min. He finished 5 rounds in 20 minutes. What is the perimeter of the park?
  1. 400
  2. 420
  3. 440
  4. 460
  5. 480

Question 5

A Mathematics competition consists of 25 questions. Each question carries 4 marks. 1 mark is deducted for every wrong or blank answer. Mary scored 75 marks. How many questions did she answer correctly?
  1. 18
  2. 19
  3. 20
  4. 21
  5. 22

Question 6

A big cube of ice loses half of its mass every 2 hours. After 8 hours its mass is 200 g. Find its original mass.
  1. 800
  2. 1600
  3. 2400
  4. 3200
  5. 4000

Question 7

Find the value of $(((((((10\div(10\div9))\div(9\div8))\div(8\div7))\div(7\div6))\div(6\div5))\div(5\div4))\div(4\div3))\div(3\div2)$.
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5

Question 8

Find the last number in the 6th row.

Question illustration
  1. 17
  2. 18
  3. 19
  4. 20
  5. 21

Question 9

The area of rectangle ABCD is 64 cm². E and F are the midpoints of AD and CD, respectively. Find the area of the shaded region.

Question illustration
  1. 18
  2. 24
  3. 32
  4. 40
  5. 44

Question 11

Evaluate $2+5+8+\cdots+98+101$.
  1. 1743
  2. 1751
  3. 1753
  4. 1800
  5. 1855

Question 12

The sum of the 5 numbers in the box is 85. Find the number in the middle of the box when the sum of the 5 numbers is 125.

Question illustration
  1. 23
  2. 25
  3. 27
  4. 29
  5. 31

Question 13

In Mathematics, $3^{2024}$ means $\underbrace{3\times3\times3\times\cdots\times3}_{2024\text{ factors}}$. What is the units digit of this product?
  1. 1
  2. 3
  3. 5
  4. 7
  5. 9

Question 14

Find the 29th digit in the string formed by concatenating the prime numbers in ascending order: 2357111317...
  1. 1
  2. 2
  3. 3
  4. 5
  5. 7

Question 15

The figure shows 3 squares and a circle. The area of the largest square is 84 cm². Find the area of the shaded region.

Question illustration
  1. 16
  2. 18
  3. 19
  4. 20
  5. 21

Question 16

How many triangles can you form using any 3 points in the figure below as vertices?

Question illustration
  1. 42
  2. 45
  3. 48
  4. 50
  5. None of the above

Question 17

A rectangle is inscribed in a square of side length 5 cm. Find the area of the shaded rectangle in cm². The diagram is not drawn to scale.

Question illustration
  1. 6
  2. 7
  3. 8
  4. 9
  5. 10

Question 18

Each number in the figure is the sum of the 2 numbers immediately below it. Find $x+y$.

Question illustration
  1. 11
  2. 12
  3. 13
  4. 14
  5. 15

Question 19

Evaluate $200+199+198-197-196+195+194-193-192+\cdots+103+102-101-100$.
  1. 244
  2. 264
  3. 278
  4. 290
  5. 300

Question 20

Given $\frac12+\frac56+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}=\frac mn$, find $m+n$, where $\frac mn$ is in simplest form.
  1. 43
  2. 53
  3. 63
  4. 74
  5. 84