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ITMC 2018 Grade 8 National Preliminary set01

Question 1

Printed positive marks are preserved per question. The source uses different blank-answer and incorrect-answer rules by section, including an optional bonus penalty; the import does not reproduce that complete official scoring scheme.

What is the value of $\dfrac{2^{20}+2^{18}}{2^{19}+2^{18}}$?
  1. $4/3$
  2. $2^{36}$
  3. 2
  4. $2^{18}$
  5. $5/3$

Question 2

Which polynomial equals $(x+20)(x+18)$?
  1. $x^2+38x+360$
  2. $x^2-38x+360$
  3. $x^2+38x-360$
  4. $-x^2+38x-360$
  5. $x^2-38x-360$

Question 3

Let $r$ be rational and $(r+\sqrt{18})^2=418+40\sqrt{18}$. Which statement is correct?
  1. $\sqrt{250}<r<\sqrt{300}$
  2. $\sqrt{300}<r<\sqrt{350}$
  3. $\sqrt{350}<r<\sqrt{400}$
  4. $\sqrt{350}<r<\sqrt{450}$
  5. $\sqrt{450}<r<\sqrt{500}$

Question 4

Triangle $ABC$ has $AB=AC$. Point $D$ is on $AB$, with $BA=3BD$; point $E$ is on $AC$, with $CA=3CE$. Which congruence condition directly proves triangles $EBC$ and $DCB$ congruent? The conditions are SSS, ASA, AAS, SAS, HL: S means side, A means angle, H means hypotenuse and L means leg. HL applies only to right triangles.
  1. HL
  2. ASA
  3. SSS
  4. SAS
  5. AAS

Question 5

Right triangles $ABC$ and $AEF$ are positioned as shown, with $AE:AB=1:2$ and $EF:BC=1:2$. What percent of the area of $ABC$ is the area of $AEF$?

Question illustration
  1. 10
  2. 25
  3. 30
  4. 40
  5. 50

Question 6

$ABCD$ is a square and $O$ is the intersection of its diagonals. Triangle $PQR$ has base $QR=20$ cm. The ratio $[ABCD]:[PQR]$ is $8:5$, and $[AOB]=256$ cm². Find the height from $P$ in cm.
  1. 16
  2. 32
  3. 64
  4. 128
  5. 256

Question 7

Jack and Jill each sell the same number of eggs daily. Jack sells 2 eggs for 5 baht and earns $a$ baht; Jill sells 3 for 7 baht and earns $b$. One day Jill sells both equal stocks together at 5 eggs for 12 baht, earning $c$. If $a:b:c=x:y:z$ for positive integers $x,y,z$, find the minimum $x+y+z$.
  1. 217
  2. 214
  3. 215
  4. 221
  5. 229

Question 8

A perfect square is a number $N=n^2$ for an integer $n$. Which digit cannot be the units digit of a perfect square?
  1. 1
  2. 2
  3. 4
  4. 6
  5. 9

Question 9

The product of the integers from 1 to 10 is 3628800. Find the smallest integer $n$ for which $\sqrt{3628800/n}$ is an integer.
  1. 1
  2. 3
  3. 5
  4. 7
  5. 9

Question 10

In a marathon, 32% of participants are adult men, 38% adult women and 20% boys; the others are girls. There are 960 adult men. Which statement is true?
  1. There are 340 boys.
  2. Girls are 12% of participants.
  3. Females are 50% of participants.
  4. There are 240 girls.
  5. None of these.

Question 11

Today is 5 August 2018. In how many days will it be 9 February 2019?
  1. 185
  2. 186
  3. 187
  4. 188
  5. 189

Question 12

At the 2018 FIFA World Cup, 32 teams are divided into eight groups A–H of four teams. In the first round each pair of teams within a group plays exactly one match. A winner gets 3 points and a loser 0; a draw gives each team 1 point. The two highest-scoring teams in each group advance to the second round.

Group E results are: Costa Rica–Serbia 0–1; Brazil–Switzerland 1–1; Brazil–Costa Rica 2–0; Serbia–Switzerland 1–2; Serbia–Brazil 0–2; Switzerland–Costa Rica 2–2. What is the total points of all four teams after the first round?
  1. 13
  2. 14
  3. 15
  4. 16
  5. 17

Question 13

At the 2018 FIFA World Cup, 32 teams are divided into eight groups A–H of four teams. In the first round each pair of teams within a group plays exactly one match. A winner gets 3 points and a loser 0; a draw gives each team 1 point. The two highest-scoring teams in each group advance to the second round.

Belgium led Tunisia 2–1 at half-time. In the second half the two teams scored four more goals in total. Which final outcome is impossible?
  1. Belgium wins by 3 goals.
  2. Belgium wins by 2 goals.
  3. Belgium wins by 1 goal.
  4. Tunisia wins by 3 goals.
  5. Tunisia wins by 1 goal.

Question 14

At the 2018 FIFA World Cup, 32 teams are divided into eight groups A–H of four teams. In the first round each pair of teams within a group plays exactly one match. A winner gets 3 points and a loser 0; a draw gives each team 1 point. The two highest-scoring teams in each group advance to the second round.

The total points in groups A–H are respectively 18, 15, 16, 17, 16, 18, 18, 17. How many first-round matches in all groups ended in a draw?

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

Question 15

Simplify $\dfrac{2a^2-4a}{3a-6}+\dfrac{2b^2-4b}{8b-16}$.
  1. $2a+2b$
  2. $2a+\frac14b$
  3. $a+b$
  4. $\frac23a+2b$
  5. $\frac23a+\frac14b$

Question 16

For a negative real number $x$, what is $\sqrt[2018]{x^{2018}}+\sqrt[2017]{x^{2017}}$?
  1. $x$
  2. $2x$
  3. $2x^2$
  4. $x^2$
  5. None of these.

Question 17

Simplify $\dfrac{x^2-4(x+3)}{(x+2)(x+3)}$.
  1. $\frac{x-6}{x+3}$
  2. $x-2$
  3. $\frac{x-2}{x+2}$
  4. $\frac{x-2}{x+3}$
  5. $x+2$

Question 18

A square has circumradius $R$ and inradius $r$. Which statement is true?
  1. $0.5r\le R\le r$
  2. $r\le R\le1.5r$
  3. $1.5r\le R\le2r$
  4. $2r\le R\le2.5r$
  5. Insufficient information.

Question 19

In isosceles triangle $ABC$, $AB=AC$ and $\angle BAC=20^\circ$. $D$ is the midpoint of $BC$ and $E$ the midpoint of $AD$. How many claims are true? (1) $\angle EBC=\angle ECB=60^\circ$; (2) $\angle ABC=\angle ACB=80^\circ$; (3) $\angle EAB=\angle EAC=10^\circ$; (4) $\angle AEB=\angle AEC=150^\circ$.
  1. 0
  2. 1
  3. 2
  4. 3
  5. 4

Question 20

Which condition does not guarantee congruence of triangles $ABC$ and $A^{\prime} B^{\prime} C^{\prime}$?
  1. $AB=A^{\prime} B^{\prime},\ \angle ABC=\angle A^{\prime} B^{\prime} C^{\prime},\ BC=B^{\prime} C^{\prime}$
  2. $\angle BAC=\angle B^{\prime} A^{\prime} C^{\prime},\ \angle ABC=\angle A^{\prime} B^{\prime} C^{\prime},\ BC=B^{\prime} C^{\prime}$
  3. $AB=A^{\prime} B^{\prime},\ AC=A^{\prime} C^{\prime},\ BC=B^{\prime} C^{\prime}$
  4. $\angle BAC=\angle B^{\prime} A^{\prime} C^{\prime},\ AB=A^{\prime} B^{\prime},\ BC=B^{\prime} C^{\prime}$
  5. Every condition A–D guarantees congruence.