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Australian AMC 2023 - Senior

Question 1

What is the value of $2023-3202$?
  1. -1221
  2. -1179
  3. 1179
  4. 1221
  5. 5225

Question 2

A parallelogram $PQRS$ has an area of $60\text{ cm}^2$ and side $PQ$ of length $10\text{ cm}$. Which length is $6\text{ cm}$?

Question illustration
  1. $RQ$
  2. $RS$
  3. $QT$
  4. $PT$
  5. $QS$

Question 3

Which one of these is equal to $57\times953$?
  1. 321
  2. 4321
  3. 54321
  4. 654321
  5. 7654321

Question 4

What is the difference between $2^5$ and $5^2$?
  1. 0
  2. 1
  3. 3
  4. 5
  5. 7

Question 5

What is the value of the angle $\theta^\circ$ in the diagram?

Question illustration
  1. $100^\circ$
  2. $110^\circ$
  3. $120^\circ$
  4. $130^\circ$
  5. $140^\circ$

Question 6

The shaded square is inscribed in the larger square as shown. What is the ratio of shaded to unshaded area in the diagram?

Question illustration
  1. $5:4$
  2. $25:24$
  3. $3:2$
  4. $7:4$
  5. $12:7$

Question 7

Jemmy multiplies together all the integers from 1 to 18. What are the last three digits of the result?
  1. 000
  2. 020
  3. 200
  4. 080
  5. 800

Question 8

A fuel tank is 40% empty. Then 40 litres of fuel is removed. The tank is now 40% full. How many litres are in a full tank?
  1. 40
  2. 100
  3. 160
  4. 200
  5. 400

Question 9

The volume $V$ of a sphere of radius $r$ is given by $V=\frac43\pi r^3$. For a sphere of volume $V=100\text{ cm}^3$, which of the following is closest to the radius?
  1. 2.9 cm
  2. 3.5 cm
  3. 5 cm
  4. 5.8 cm
  5. 10 cm

Question 10

If I add 3 consecutive odd integers, I get a total of $9m+3$. The largest of these 3 integers is
  1. $3m-3$
  2. $3m-1$
  3. $3m$
  4. $3m+1$
  5. $3m+3$

Question 11

The value of $(\sqrt{24}+\sqrt{54})^2$ is
  1. 140
  2. 150
  3. 160
  4. 170
  5. 180

Question 12

In a group of 6 people there are 3 pairs of twins. How many 3-member committees can be chosen that do not contain any pair of twins?
  1. 0
  2. 8
  3. 12
  4. 24
  5. 48

Question 13

Assuming $a>b>0$, the expression $\frac{a^{-1}-b^{-1}}{a^{-2}-b^{-2}}$ can be written as
  1. $\frac{b-a}{ab}$
  2. $\frac{b+a}{ab}$
  3. $\frac{ab}{b+a}$
  4. $\frac{a^2-b^2}{a-b}$
  5. $a-b$

Question 14

A bag contains red and yellow balls such that the ratio red : yellow is $5:7$. Then 10 balls of each colour are removed and the ratio changes to $5:8$. How many balls were originally in the bag?
  1. 48
  2. 60
  3. 72
  4. 84
  5. 96

Question 15

In the solution to this number puzzle, whenever there are three numbers in a straight line, the middle number is the sum of the other two. What is the value of $x$?

Question illustration
  1. $\frac12(a+b+c)$
  2. $\frac12(b-a-c)$
  3. $\frac12(a+b-c)$
  4. $\frac12(a-b+c)$
  5. $\frac12(b+c-a)$

Question 16

If $f(x)=5+x$ and $g(x)=7-x$, then $f(g(x))-g(f(x))$ equals
  1. $10-x$
  2. 7
  3. $x+2$
  4. 10
  5. $2x-2$

Question 17

The hypotenuse of a right-angled triangle has length $6\text{ cm}$. The perimeter of the triangle is $14\text{ cm}$. What is the area of the triangle in square centimetres?
  1. 7
  2. 12
  3. 14
  4. 21
  5. 24

Question 18

I have two identical dice, each with faces $1,\frac12,\sqrt3,\frac1{\sqrt3},\frac1{\sqrt2}$ and $\frac{\sqrt3}{2}$. I roll both dice and multiply the two numbers rolled, then simplify my answer. What is the probability that this product is rational?

Question illustration
  1. $\frac19$
  2. $\frac16$
  3. $\frac12$
  4. $\frac5{18}$
  5. $\frac7{18}$

Question 19

How many distinct pairs $(x,y)$ satisfy $x^2+y^2<50$ if $x$ and $y$ are both positive integers with $x>y$?
  1. 15
  2. 13
  3. 11
  4. 9
  5. 8

Question 20

A $15\text{ cm}\times20\text{ cm}$ rectangle is cut into two triangles. One triangle is rotated and placed on top of the other triangle as shown to form a concave pentagon. What is the perimeter of the pentagon?

Question illustration
  1. 80 cm
  2. 84 cm
  3. 93 cm
  4. 96 cm
  5. 105 cm