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ITMC 2018 Grade 10 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.

Let $A,B$ be sets. Which set expression is different from the others? A prime denotes complement.
  1. $(A-B)^{\prime}$
  2. $A^{\prime}\cup B$
  3. $(B^{\prime}-A^{\prime})^{\prime}$
  4. $B-A$
  5. $(B^{\prime}\cap A)^{\prime}$

Question 2

Finite set $A$ has no proper subset, and $A\in B$. What is the least number of elements of $A\cup\mathcal P(B)$? Here $\mathcal P$ denotes the power set.
  1. 0
  2. 1
  3. 2
  4. 3
  5. 4

Question 3

$A=\{1,3,4\}$, $B=\{1,\{3\},\{4\},\{1,3,4\}\}$ and $C=\{\{4\},A,B\}$. How many elements are in $A\cup B\cup C$?
  1. 9
  2. 8
  3. 7
  4. 6
  5. 5

Question 4

Let $S=\{a,b,\{a\},\{a,b\}\}$ and $A=\{x\mid x\subset S\text{ and }\{a\}\subset x\}$. What is $n(A)$? The source uses the symbol $\subset$.
  1. 15
  2. 14
  3. 8
  4. 7
  5. 4

Question 5

$p\to(q\to r)$ is false. Consider (1) $p\leftrightarrow(q\leftrightarrow r)$; (2) $p\land(q\land r)$; (3) $p\lor(q\lor r)$. Which are false?
  1. (1) and (2) only
  2. (1) and (3) only
  3. (2) and (3) only
  4. All three
  5. Fewer than two are false

Question 6

Which proposition is not logically equivalent to the others?
  1. $(p\lor\neg p)\land q$
  2. $q\lor(p\land\neg p)$
  3. $(p\leftrightarrow\neg p)\leftrightarrow\neg q$
  4. $(p\to\neg p)\to\neg q$
  5. $q\land q$

Question 7

Consider (1) $\neg p\to(q\lor r)$; (2) $(\neg q\land\neg r)\to p$; (3) $p\lor q\lor r$. Which statement is true?
  1. Only (1),(2) are equivalent.
  2. Only (1),(3) are equivalent.
  3. Only (2),(3) are equivalent.
  4. No pair is equivalent.
  5. All three are equivalent.

Question 8

Find the negation of $\forall x\lt 0\ \exists y\lt 0\ [x\lt y\to x^2>y^2]$.
  1. $\exists x\lt 0\ \forall y\lt 0\ [x\ge y\to x^2\le y^2]$
  2. $\exists x\lt 0\ \forall y\lt 0\ [x\lt y\land x^2\le y^2]$
  3. $\exists x\ge0\ \forall y\ge0\ [x\ge y\to x^2\le y^2]$
  4. $\exists x\ge0\ \forall y\ge0\ [x\lt y\land x^2\le y^2]$
  5. $\exists x\ge0\ \forall y\ge0\ [x\ge y\lor x^2>y^2]$

Question 9

How many real solutions satisfy $\left|\left||x-2561|+2561\right|-2561\right|=543$?
  1. 1
  2. 2
  3. 3
  4. 4
  5. More than 4

Question 10

Find the solution set of $x^2(x-2)\le4(x-2)$.
  1. $(-\infty,-2]$
  2. $[-2,\infty)$
  3. $[-2,2]$
  4. $(-\infty,2]$
  5. None of these.

Question 11

Given $a-b>a$ and $a+b\lt b$, which statement must be true?
  1. $a\lt b$
  2. $b\lt a$
  3. $a\lt b\lt 0$
  4. $a\lt 0$ but $b>0$
  5. $a\lt 0$ and $b\lt 0$

Question 12

$2^x=\sqrt[3]{20}-\sqrt[3]{18}$ and $2^y=\sqrt[3]{400}+\sqrt[3]{360}+\sqrt[3]{324}$. Which relation holds?
  1. $y=1-x$
  2. $y=2-x$
  3. $y=1/x$
  4. $y=2/x$
  5. None of these.

Question 13

Of 40 surveyed students,36 entered both the fifth and sixth Thailand Mathematics Contests. Among these 36,24 won gold at the fifth and 25 at the sixth. What is the least number who won gold at both?
  1. 11
  2. 13
  3. 17
  4. 24
  5. 25

Question 14

For propositions $a,b,c$, which choice for $P$ makes $((a\land b)\land(b\to c))\to P$ a tautology?
  1. $\neg b$
  2. $a\land\neg c$
  3. $c\to\neg b$
  4. $\neg a\lor(b\land c)$
  5. $(a\lor c)\land\neg b$

Question 15

$\forall x\ \exists y\ [(x-2)(2-y)>0]$ is true. Which set can be the common domain of x and y?
  1. $\{0\}$
  2. $\{1\}$
  3. $\{3\}$
  4. $\{0,1\}$
  5. $\{1,3\}$

Question 16

Real $x$ satisfies $1/x>-5$ and $1/x\lt 2$. Which statement describes the solutions?
  1. $-1/5\lt x\lt 1/2$
  2. $-1/2\lt x\lt 5$
  3. $x>1/2$
  4. $x>1/2\text{ or }-1/5\lt x\lt 0$
  5. $x>1/2\text{ or }x\lt -1/5$

Question 17

Which ordering is true?
  1. $\frac{12}7\lt \frac{\sqrt6+1}2\lt \sqrt3$
  2. $\frac{12}7\lt \sqrt3\lt \frac{\sqrt6+1}2$
  3. $\sqrt3\lt \frac{\sqrt6+1}2\lt \frac{12}7$
  4. $\frac{\sqrt6+1}2\lt \sqrt3\lt \frac{12}7$
  5. $\frac{\sqrt6+1}2\lt \frac{12}7\lt \sqrt3$

Question 18

Suppose $3x^2+9x^2+kx-12$ is divisible by $x+3$, with real k. Which polynomial divides $3x^2-9x^2+kx-12$? Both leading exponents are printed as 2.
  1. $3x^2-4$
  2. $3x^2+4$
  3. $3x^2-x+4$
  4. $3x-4$
  5. $3x+4$

Question 19

Real $x$ satisfies $(x+1)(x+2)(x+3)+(x+1)(x+2)+x+4=0$. Find the sum of all possible real x.
  1. $-7$
  2. $-6$
  3. $-4$
  4. $-3$
  5. $-1$

Question 20

Real $a,b$ satisfy $a^2+25a+61=0$ and $b^2+25b+61=0$. Find $(a+3)(b+3)$.
  1. $-149$
  2. $-5$
  3. $145$
  4. $167$
  5. $217$