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BBB 2021 - Grade 4 - Preliminary Round

Question 2

Find the least common multiple of 16 and 18.
  1. 36
  2. 32
  3. 288
  4. 144

Question 3

Find the highest common factor of 72 and 81.
  1. 8
  2. 9
  3. 3
  4. 1

Question 4

Given an arithmetic sequence: 7, 12, 17, 22, …, 127. How many numbers are there?
  1. 25
  2. 24
  3. 120
  4. 134

Question 5

A 3-digit number is divided by 7 to get a remainder of 1. Find the minimum value of this 3-digit number.
  1. 107
  2. 99
  3. 106
  4. 105

Question 6

Find the average of these 6 numbers: 22, 58, 39, 47, 21, 23.
  1. 35
  2. 36
  3. 37
  4. 38

Question 7

Refer to the figure below, how many triangles are there?

Question illustration
  1. 19
  2. 21
  3. 17
  4. 20

Question 8

Now there are 2 numbers. Their sum is 252. The bigger one is 11 times as the smaller one. Find the value of the smaller one.
  1. 20
  2. 231
  3. 22
  4. 21

Question 9

The sum of ages of father and mother is 93 this year. If father’s age 3 years ago is equal to mother’s age 4 years later, how old is father this year?
  1. 50
  2. 47
  3. 54
  4. 48

Question 10

Nick has 21 \$1 coins and \$5 coins worth \$81 in total. How many \$5 coins does Nick have?
  1. 30
  2. 6
  3. 15
  4. 11

Question 11

Today is Wednesday. Which day of the week will 577 days be later?
  1. Saturday
  2. Sunday
  3. Thursday
  4. Friday

Question 12

If $2\oplus2=2+3$ and $3\oplus4=3+4+5+6$. Find the value of $6\oplus5$.

Editorial interpretation: take $a\oplus b$ to mean the sum of $b$ consecutive integers beginning with $a$. The examples suggest this rule but do not uniquely define an arbitrary operation. The answer below is conditional on this intended rule.
  1. 11
  2. 30
  3. 35
  4. 40

Question 13

In Mathematics Exam, the average marks for boys and girls are 78 and 62 respectively. The numbers of boys and girls are 25 and 15 respectively. What is the average mark?
  1. 68
  2. 70
  3. 74
  4. 72

Question 14

We have 4 masses with weight 1g, 2g, 5g and 6g. After we give up one of them, we cannot measure 9g, and 11g anymore. What is the weight of the mass given up? (Masses can only place on the same side)
  1. 1g
  2. 5g
  3. 6g
  4. 2g

Question 15

Refer to the following figure, how many rectangles are there with 2 black dots?

Question illustration
  1. 24
  2. 12
  3. 36
  4. 48

Question 16

If a 9-digit number $\overline{61314826A}$ is divisible by 9, find the value of $A$.
  1. 3
  2. 9
  3. 4
  4. 5

Question 17

Find the value of $688\div125+223\div125+464\div125$.
  1. 15
  2. 13
  3. 11
  4. 12

Question 18

Numbers are drawn from 58 integers 1 to 58. At least how many numbers are drawn at random to ensure that there are two numbers whose sum is 25?
  1. 44
  2. 45
  3. 46
  4. 47

Question 19

The difference between A and B is 70. A is 15 times of B. Find the value of A.
  1. 85
  2. 75
  3. 80
  4. 70

Question 20

If $A\times B=667$ and $A,B$ are positive integers, find the minimum value of $A+B$.
  1. 52
  2. 668
  3. 50
  4. 48