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SASMO 2022 Grade 9

Question 1

Platform scoring: initial 0; Q1–15: 2 points each; Q16–25: 4 points each; wrong/blank: 0; maximum 70. Official reference: initial 15; Section A correct +2, wrong −1, blank 0; Section B correct +4, wrong/blank 0; maximum 85.

Find the value of $56\times7\times125\times51$.
  1. 2500000
  2. 2499000
  3. 249000
  4. 249900
  5. None of the above

Question 2

How many prime numbers $p$ satisfy $\dfrac{p+2}{2}\le\dfrac{2p-1}{2}+\dfrac23<3\dfrac12$?
  1. 0
  2. 1
  3. 2
  4. Infinitely many
  5. None of the above

Question 3

Which of the following has the greatest value?
  1. $3^{13}$
  2. $9^5$
  3. $27^4$
  4. $81^3$
  5. $243^2$

Question 4

How many digits are there in $2022\times5^{2022}\times64^{337}$?
  1. 2022
  2. 2024
  3. 2025
  4. 2026
  5. None of the above

Question 5

How many positive even 2-digit numbers are divisible neither by 5 nor by 7?
  1. 15
  2. 20
  3. 30
  4. 45
  5. None of the above

Question 6

How many factors of 540000 are perfect cubes?

Interpretation: As in the source, factors mean positive integer divisors; 1 is a perfect cube.
  1. 3
  2. 5
  3. 7
  4. 8
  5. None of the above

Question 7

If the product of four consecutive positive integers is 2961840, what is their sum?
  1. 166
  2. 164
  3. 162
  4. 160
  5. None of the above

Question 8

Given that $12^8$ is the 9-digit number $4a9\,981\,69b$, find the product $ab$.

Interpretation: Here a and b are decimal digits, and ab means a multiplied by b.
  1. 2
  2. 6
  3. 8
  4. 12
  5. None of the above

Question 9

Find the last two digits of $7^{2022}$.
  1. 07
  2. 49
  3. 43
  4. 01
  5. None of the above

Question 10

In the diagram, square $ABCD$ is inscribed in a circle. Its diagonals meet at $O$. Points $E,F,G,H$ are the midpoints of $AO,BO,CO,DO$, respectively. What fraction of the circle’s area is shaded?

Interpretation: The shaded region is inside ABCD and outside EFGH. The four inner vertices are the named midpoints.

Question illustration
  1. $\dfrac1{2\pi}$
  2. $\dfrac3{2\pi}$
  3. $\dfrac1{4\pi}$
  4. $\dfrac3{4\pi}$
  5. None of the above

Question 11

The integer $b$ is a multiple of 3 but not a multiple of 6. Which of the following is NOT odd?
  1. $b+24$
  2. $b-36$
  3. $7b+8$
  4. $3b+3$
  5. None of the above

Question 12

A game begins with four piles containing 20, 22, 25 and 27 marbles. On each turn a player takes 3 marbles from the largest pile and gives one to each of the other three piles. How many marbles are in the smallest pile after the 2022nd turn?
  1. 20
  2. 22
  3. 23
  4. 24
  5. None of the above

Question 13

What is the sum of the digits of $B=6666666^2-3333333^2$?
  1. 54
  2. 63
  3. 70
  4. 77
  5. None of the above

Question 14

How many integers between $10^3$ and $10^6$ have digit sum 2?
  1. 8
  2. 9
  3. 14
  4. 15
  5. None of the above

Question 15

In the diagram, $\angle ABC=\angle BCD=\angle DEF=\angle FAB=90^\circ$, $AB=22$, $BC=18$, $DE+FE=28$ and $AF=CD$. Find the area of $ABCDEF$.

Question illustration
  1. 200
  2. 202
  3. 204
  4. 210
  5. None of the above

Question 16

Towns A and B are 1.26 km apart. At 9:00 a.m., Aaron starts cycling from A to B at 72 metres per minute, while Jeremy starts from B to A at 108 metres per minute. At 9:04 a.m., Kyle starts from A to B at 144 metres per minute. What is the distance, in metres, between Kyle and Jeremy when Aaron first meets one of them?

Interpretation: All three travel along the same route at their stated constant speeds. “Meets” means after Aaron starts; Kyle’s later departure is not an encounter at 9:00.

Answer format: an integer without units. Leading zeros are optional; the source uses four digit boxes.

Question 17

The product $999n$ contains no digit 9. Find the smallest positive integer $n$ satisfying this condition.

Answer format: an integer without units. Leading zeros are optional; the source uses four digit boxes.

Question 18

Find the smallest positive multiple of 19 whose digits add to 23.

Answer format: an integer without units. Leading zeros are optional; the source uses four digit boxes.

Question 19

In a classroom, each student shook hands with 4 girls and 6 boys. The number of handshakes between students of the same gender was 7 more than the number between students of opposite genders. How many boys were in the classroom?

Interpretation: No student shakes their own hand, and any pair shakes hands at most once; “4 girls and 6 boys” refers to other students.

Answer format: an integer without units. Leading zeros are optional; the source uses four digit boxes.

Question 20

The 2022nd term of the sequence below is $m/n$ in lowest terms, with $\operatorname{HCF}(m,n)=1$. Find $n-m$. $$\frac12,\frac13,\frac14,\frac24,\frac15,\frac25,\frac16,\frac26,\frac36,\frac17,\frac27,\frac37,\ldots$$

Interpretation: Continue by increasing denominator d = 2, 3, 4, …; for each d list numerators 1 through floor(d/2) in order. Repeated equal fractions remain separate terms, and term 1 is 1/2.

Answer format: an integer without units. Leading zeros are optional; the source uses four digit boxes.