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SASMO 2021 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 rules: initial 15; Section A correct +2, wrong −1, blank 0; Section B correct +4, wrong/blank 0; maximum 85.

Calculate $\dfrac{2020+2019\times2021}{2020\times2021-1}+\dfrac{2021+2020\times2022}{2021\times2022-1}$.
  1. 2021
  2. 2020
  3. 2019
  4. 2
  5. None of the above

Question 2

Tom and Michael buy ice cream under a promotion. Tom may choose vanilla, mango, strawberry or mint. Michael may choose blueberry, Milo, chocolate or matcha. Each combination costs the amount in the table; for example, vanilla with Milo means both pay USD 3.00 for the ice cream. Which flavour should Tom choose to spend the minimum amount regardless of Michael’s choice?

Interpretation: Use the source’s intended worst-case interpretation: minimize the highest price Tom might have to pay.

Question illustration
  1. Vanilla
  2. Mango
  3. Strawberry
  4. Mint
  5. Milo

Question 3

Given $8\lt 2y+6\lt 20$ and $0\le x+10\le10$, find the greatest possible value of $xy$.
  1. 70
  2. 60
  3. 63
  4. 54
  5. None of the above

Question 4

If $a$ is positive and $b=2\sqrt a\times a-1$, which statements are always true?

I. $b$ is an odd number.

II. $b$ is positive.

III. $b$ is an integer.
  1. I only
  2. II only
  3. III only
  4. I and II only
  5. None of the above

Question 5

Figure 1 is a stack map: each number gives the number of cubes stacked at that position. Figure 2 shows those cubes and Figure 3 shows their front view. Which option is the front view for the stack map in Figure 4?

Question illustration

Question illustration
  1. Diagram A
  2. Diagram B
  3. Diagram C
  4. Diagram D
  5. Diagram E

Question 6

Albert, Brad and Chris played 10 games. All three played every game, with no other participants and no ties. In each game, the winner earned 10 points, the first runner-up 4 points and the second runner-up 1 point. Albert earned 73 points and Brad 49 points in total. How many points did Chris earn?
  1. 28
  2. 49
  3. 73
  4. 150
  5. None of the above

Question 7

January 1, 2021 is a Friday. Which day of the week occurs the most throughout 2021?
  1. Tuesday
  2. Thursday
  3. Saturday
  4. Sunday
  5. None of the above

Question 8

Mary has 200 pieces of candy for 8 students standing in a straight line. Starting with student 1, she moves along the line and gives each student one piece when she stops. At student 8 she turns around and continues giving candy on the way back, repeating until all candy is gone. Which student receives the last piece?

Interpretation: A student at either end receives one piece per visit; turning around does not give that same student a second immediate piece.
  1. 1st student
  2. 3rd student
  3. 4th student
  4. 6th student
  5. None of the above

Question 9

Find the last two digits of $2021^{2021}$.
  1. 01
  2. 21
  3. 41
  4. 61
  5. None of the above

Question 10

In 205,000, the last three zeros are terminal zeros; the zero after the digit 2 is not. How many terminal zeros are in $1\times2\times3\times\cdots\times129\times130$?
  1. 26
  2. 31
  3. 32
  4. 130
  5. None of the above

Question 11

How many pages are in a book if its page numbers are written using fifty-five occurrences of the digit 1?

Interpretation: Pages are numbered consecutively from 1 to the last page, with no omitted page numbers.
  1. 120
  2. 121
  3. 122
  4. 50
  5. None of the above

Question 12

Four boxes contain one item each: a red pencil, a green pencil, a blue pen and a black pen. Their labels say:

- Box 1: This box does not contain the red pencil.
- Box 2: The blue pen is in either Box 1 or Box 3.
- Box 3: The black pen is in Box 1.
- Box 4: This box contains the green pencil.

Boxes containing pens have true labels; boxes containing pencils have false labels. Which box contains the blue pen?
  1. Box 1
  2. Box 2
  3. Box 3
  4. Box 4
  5. Impossible to determine

Question 13

In the diagram, $ABCD$ and $CEFG$ are squares. $H$ is the intersection of lines $AE$ and $CG$. If $CE=10$, find the area of the shaded region.

Question illustration
  1. 48
  2. 50
  3. 52
  4. 100
  5. None of the above

Question 14

Derrick spent USD 200 in 5 days. Each day he spent no more than on the previous day, and each daily amount was an integer number of dollars. What is the smallest possible total spent on days 1, 3 and 5?

Interpretation: A daily amount may be zero; spending is nonnegative, as in the source’s example.
  1. 20
  2. 40
  3. 50
  4. 100
  5. None of the above

Question 15

A very large multiple of 76 has 76 as its last two digits and has 28 positive integer factors. Express it as $n\times a^b$, where $n,a,b$ are positive integers. What is the lowest possible value of $n+a+b$?
  1. 104
  2. 80
  3. 79
  4. 34
  5. None of the above

Question 16

What is the least number of whole numbers that must be selected from $\{1,2,3,\ldots,36,37\}$ to guarantee that one selected number is divisible by another?

Interpretation: Select distinct entries, without replacement. The guarantee must hold for every possible selection.

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

Question 17

A multiple of 4 and the sum of all its digits add up to 2021. Find the number.

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

Question 18

Two whole numbers $x,y$ have HCF 4 and LCM 5040. Given $x\le y$, how many pairs $(x,y)$ are there?

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

Question 19

The sum of 10 positive integers is 1001. What is the largest possible HCF of the 10 numbers?

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

Question 20

In triangle $ABC$, $\angle C=120^\circ$ and $BC=2AC$. $D$ is the midpoint of $BC$, and $E$ is on side $AB$ such that $ED\perp BC$. If $BE=20$, find $AE$.

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