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HKIMO 2026 Grade 8 National Preliminary Set 05

Question 1

A test has 25 questions, worth 2 points for each correct answer. At least how many students must take it to guarantee that four receive the same score?

Editorial scoring convention for this word problem: each incorrect or unanswered question earns zero points.
  1. 79
  2. 76
  3. 101
  4. 105

Question 2

John travels 13 km northwest, then 12 km northeast, then 4 km southeast. How far is he from his starting point?
  1. 15 km
  2. 29 km
  3. 21 km
  4. 5 km

Question 3

Given $\overline{abcd}+\overline{badc}=17688$, find $a+b-c-d$.
  1. 9
  2. 8
  3. 7
  4. 10

Question 4

It is 6 o’clock. How many minutes until the minute hand and hour hand first overlap?
  1. $33\frac{8}{11}$
  2. $32\frac{5}{11}$
  3. $32\frac{8}{11}$
  4. $33\frac{5}{11}$

Question 5

There are 13 white, 11 yellow and 14 brown chopsticks mixed together. What is the least number to draw without looking to guarantee two non-yellow pairs?

Editorial convention: each pair consists of two chopsticks of the same colour.
  1. 13
  2. 14
  3. 15
  4. 16

Question 6

Find $y$ if $|2x+6y+8|+|x-3y+4|=0$.
  1. -4
  2. 0
  3. 4
  4. 2

Question 7

Let $a$ be constant. The coefficient of $x$ in $(2x-a)(x^2-4x)$ is 20. Find $a$.
  1. 5
  2. -5
  3. 80
  4. -80

Question 8

How many negative integers $x$ satisfy $-97\le7x+3\le32$?
  1. 15
  2. 19
  3. 14
  4. 18

Question 9

Given that $x-2$ is a factor of $x^3-2x^2+3x+m$, find $m$.
  1. 6
  2. -6
  3. 22
  4. 10

Question 10

Given $f(x)=ax^2+bx+c$, $f(-1)=3$, $f(2)=18$ and $f(-2)=6$, find $f(1)$.
  1. 15
  2. -3
  3. 3
  4. 9

Question 11

Find the remainder when $2024^{2024}$ is divided by 5.
  1. 4
  2. 2
  3. 3
  4. 1

Question 12

If $A=30!\div3^n$ is an integer, find the largest value of $n$.

Editorial domain convention: n is a nonnegative integer exponent.
  1. 12
  2. 10
  3. 14
  4. 13

Question 13

Find the units digit of $A=1+7+7^2+7^3+\cdots+7^{99}+7^{100}$.
  1. 1
  2. 3
  3. 7
  4. 9

Question 14

How many positive integers less than 65 are coprime to 65?
  1. 45
  2. 48
  3. 52
  4. 47

Question 15

Find the number of positive divisors of 35000.
  1. 30
  2. 40
  3. 50
  4. 60

Question 16

Right triangles satisfy $\triangle ABC\sim\triangle FED$, with legs $AB=5$ and $BC=12$. Find $DF:EF$.
  1. $\frac{13}{5}$
  2. $\frac{17}{5}$
  3. $\frac{12}{5}$
  4. $\frac{13}{12}$

Question 17

On a coordinate plane, $A=(9,4)$, $B=(1,3)$ and $C=(9,8)$. Find the area of triangle ABC.
  1. 20
  2. 12
  3. 16
  4. 24

Question 18

A triangle has side lengths 13, 20 and x, where x is an integer. How many possible values of x are there?
  1. 27
  2. 24
  3. 26
  4. 25

Question 19

An exterior angle of a regular n-sided polygon is $(2n+16)^\circ$. Find n.
  1. 8
  2. 10
  3. 16
  4. 18

Question 20

How many diagonals does a convex 80-sided polygon have?
  1. 3080
  2. 3160
  3. 6320
  4. 3120