SEAMO 2026 — Paper B — SET 3 — Organizer self-practice

Find the missing number in the pattern below.

$2,7,17,32,52,(\quad),107,\ldots$

Find the number of triangles in the figure shown below.

The value of $\frac{1}{1\times3}+\frac{1}{3\times5}+\frac{1}{5\times7}+\frac{1}{7\times9}$ is $\frac{m}{n}$ in lowest terms. Find the value of $m+n$.

A number $m$ is divided by 10, before it is added to 80. It is then multiplied by 3. Finally 85 is subtracted from the product; the result is 200. Find $m$.

The figure below is made by removing some cubes from a $3\times3\times3$ cube. How many cubes are there? (Assume that all hidden cubes have not been removed.)

What is the ones digit of $\underbrace{2\times2\times\cdots\times2}_{67\text{ factors of }2}-1$?

There are 20 ducks, chickens and goats on a farm. The farmer counted 48 legs on all his animals. Given that there are the same number of ducks and chickens, find the number of goats.

A new operation is defined by $a\nabla b=a+(a+1)+(a+2)+(a+3)+\cdots+(a+b)$. Find $x$ if $x\nabla8=126$.

In the figure, lines $AC$ and $BD$ divide quadrilateral $ABCD$ into four triangles. The areas of $\triangle ADO$, $\triangle CDO$, $\triangle ABO$ are $2$, $4$ and $3$ cm$^2$, respectively. Find the area of $ABCD$ in cm$^2$.

The side length of a square is increased by 50%. By how many percent is its area increased?

The product of a number multiplied by itself is called a square number. $1260\times m$ is a square number. Find the smallest positive integer $m$.

The figure below consists of a circle of radius 5 cm and a right-angled isosceles triangle. Find the area of the shaded regions.

Mark writes his father's age, followed by his own age, thus forming a four-digit number $\overline{abcd}$. When Mark subtracts the difference of their ages from $\overline{abcd}$, the result is 3786. How old is Mark?

Find the interior angle of the regular pentagon shown below.

In a certain month some years ago, there were five Tuesdays, and the sum of their dates was 85. On which day of the week was the 19th of that month?

Find the value of $12345654321\times(1+2+3+4+5+6+5+4+3+2+1)$.

How many numbers in the sequence $1,2,3,4,\ldots,29,30$ are not divisible by 5?

Evaluate $1+2-3+4+5-6+\cdots+97+98-99+100$.

In a magical kingdom there are two kinds of talking mammals: zebras and giraffes. Giraffes always tell the truth, while zebras always lie.

A: D and I are different species.

B: D is a giraffe.

C: A is a zebra.

D: Only one of us is a zebra.

There are ____ zebras and ____ giraffes.

Each big ball is $1\frac13$ times the weight of a small ball. Which of the following numbers of balls can be added to the right-hand side of the scale to make it balanced?