1. Two numbers have the product of 9315. If the product is five times as
same as the greater number. The smaller number is ..........
Key: 5
2. The sum of 2 numbers is 807. If one of the number is 399, what is
the other number? Answer: the other number is……
Key: 408
3. Toan took 4 weeks to complete his project. Lina took 23 days to complete
her project. How much days faster did Lina take to complete her project
than Toan?
Key: 5
4. The smallest 3 – digit even number can be formed using all the digits 4; 2
and 3 that divided by 6. What is the quotient?
Key: 39
5. Gina is 2 years 3 months older than her sister. Her sister is 7 years 8
months old? How old is Gina?
Key: 9y 11m
6. Mark has 49 stamps. James has 289 more than Mark. Alvin has 39 stamps
less than James. How many stamps do James and Alvin have altogether?
Key: 637
7. What is the smallest odd number that can be formed using all the digits 3;
6; 1 and 4.
Key 1463
8. Mr Dung finished polishing his car at 1.25 pm. He took 2 hours and 25
minutes to finish this task. At what time did start polishing his car?
Key: 10h 50
9. Jaya is 19 years old. Six years ago, her mother was three times as old as
her. How old is her mother now?
Key: 45
10.When a pail is half filled with water, its weight is 2 kg 500g the pail when
empty weighs only 1 kg. What is the weight of the pail when it is
completely filled with water?
Key: 1kg 500g
11.What is the place value of digit 5 in this number 12589?
12.Find the number that contains 4 ten thousands, 3 hundreds, 2 tens and 1
ones.
Key:

13.6 is just after of 5 and 5 is just before 6. What is the product of just after
and just before of 10?
Key: 99
14.What is the smallest even number such that it is the product of 9 and a
number?
Key:0
15.Anna has 206 stickers and Mary has 78 stickers. How many stickers must
Anna give to Mary so that they have the same number of stickers?
Key: 64
16.Mr Junior bought 1 magazine, 1 book and 1 pen. The pen costs 5 dollar.
The book costs 31 dollar more than the pen. The magazine costs twice as
much as the book. How much did he spend on the three things?
Key: 113
17.If A is divided by 9 then the sum of the quotient and 9 is the greatest 2 –
digit number. Find the value of A.
Key: 810
18.If A is the sum of the greatest 2 - digit - number and the smallest 3 - digit number then A =
Key: 199
19.Angela is learning to play the violin. She practices 50 minutes a day on
Tuesday and Thursday. On Saturday she practices for one and a half
hours. How much times per week Angela spend practicing violin?
Key: 190 phut
20.The total weight of 3 apples is equal to that of 4 bananas, and the total
weight of 5 bananas is equal to that of 6 oranges. How many apples have
the same total weight as 24 oranges?
21.Mary reads four books every month. She is busy and reads only one book
on March. On September, she takes a break and does not read any books.
What is the number of books that Anna reads in one year?
22.Bob buys three times as many apples as Peter. Mia buys 7 apples more
than Bob and 19 apples more than Peter. How many apples do they buy
together? Key: 49
23.How many natural numbers between 1000 and 4000 are there for which
the thousands digit equals the sum of the other three digits?
24.Five students do an exam with a maximum score of 50. The scores of four
of the students are 41, 44, 46 and 49. The average of five students' scores
is the same as the score of the fifth student. The score of the fifth student
is key: 45

25.A fraction is equal to 2/5 . The sum of its denominator and its numerator
is 91. What is the difference between the denominator and numerator of
this fraction?
Key:39
26.2.1. The perimeter of a rectangular field is 100m. The length increases by
1/3 then the perimeter is 120m. Find the area of the field.
Key: 600m2

2.2. The perimeter of a rectangular field is 110m. If the width increases by
5m and the length decreases by 5m, the area is unchanged. Find the area of
the field.
2.4. If the width of a rectangle increases to be equal to the length, the area
increases by 20m2. If the length decreases to be equal to the width, the area
decreases by 16m 2. Find the area.

2.5. The area of a rectangle is 135m2. The width equals 3/5 of the length. Find
the perimeter.

2.6. The perimeter of a rectangular yard is 110m. If the width increases by 5m,
the yard becomes a square. Find the area of the rectangular yard.

2.7. The perimeter of a rectangle is 150m. If the length decreases by 10m and
the width increases by 5m, the new length is 4 times of the new width. Find the
area of the rectangle.

5.1. Find the average of all whole numbers from 1 to 17
Key: 9

5.2. Mai made cakes in 2 days. On the first day, she made 50 cakes. On the
second day, she made 20 cakes more than the first day. How many cakes
did she make on each day on average?
Key: 60
5.3. A group of truck carried goods in 2 trips. In the first trip, there were 5
trucks and each carried 315kg of goods. In the second trip, there were 4
trucks and each carried 225kg of goods. How many kilograms of goods
did each truck carry on average?
Key:275kg
5.4. 3 groups of men planted trees. Group 1 had 3 men and each planted 72
trees. Group 2 had 4 men and each planted 65 trees. Group 3 had 3 men
and each planted 68 trees. How many trees did each man plant on
average?
Key:68
5.5. Tri, Manh, Tai collected waste paper. Tri collected 24kg, Manh
collected 20kg and Tai collected 4kg more than Tri. How many
kilograms of waste paper did each boy collect on average?
Key: 24
5.6. After 3 Math tests, Binh's average score was 5. What score does he
need to score in the next test so that his average Math score is 6?
Key:3
5.7. A car travelled in 6 hours. During the first 3 hours, it travelled 42km in
each hour. In the next 2 hours, it travelled 38km in each hour. How long
did it travel in the last hour? Given that it travelled 41km per hour on
average.
Key: 44km
5.8. Find the average of all 2-digit odd numbers greater than 79.
Key:90
5.9. Find the average of all 3-digit even numbers.

Key: 549
6. Các bài toán về số
Definition: digit (chữ số), fraction (phân số), numerator (tử số),
denominator (mẫu số), whole number (số tự nhiên), odd (lẻ), even (chẵn),
divisible (chia hết), remainder (số dư), ones (đơn vị), tens (chục), hundreds
(trăm), thousands (nghìn)
6.1. A number has 80 thousands, 6 hundreds and 2 ones. What is the
number?
6.2. When writing digit 5 to the left of a 3-digit number, how many ones is
the new number more than the old one?
6.3. The sum of all digits of a 3-digit number is 26. When swapping 2 digits
in hundreds and ones places, the number does not change. Find the
number.
6.4. How many odd numbers are there in a series of whole numbers from
325 to 796?
6.5. A = 1 x 2 x 3 x 4 x 5 x 6 + 63 : 9. Without calculating, find the last digit
of A.
6.6. How many even numbers are there in a series of whole numbers from
324 to 987?
6.7. Write number 862305 in words.
6.8 what is the smallest 3-digit number which has digit 3?
6.9. What is the largest 4-digit number which has digit 4?
6.10. What is the smallest 5-digit number which has all digits different from
each other?
Key:10234
6.11. How many 3-digit numbers are made from 3; 1; 8 such that all digits in
the number are different from each other?
key:6
6.12.
When writing all whole numbers from 1 to 39, how many digits are
there?
Key:69

7. Toán đố
7.1. Mr. Manh, a farmer, harvested 476kg of rice. Mr. Hung, a farmer,
harvested 36kg more than Mr. Manh. How many kilograms of rice did
the 2 men harvest?
Key:988kg
7.2. There are 2 oil tanks. If 15l of oil is moved from the first tank to the
second, the first tank's oil is 1/3 of the second's. Then 5l of oil is taken
away from the second tank and it now has 31l of oil. How much oil in
each tank at first?
Key:1: 27
2:21
7.3. A factory produces 875 fans in 5 days. How many fans does it produce
in 7 days?
Key:1225
7.4. A truck carries 7500kg of sand the first time. The second time, it carries
600kg less than the first time. How many kilograms of sand does it carry
in 2 times?
Key:14400kg
7.5. There are 4 packs of candies and 6 packs of biscuits. Each candy pack is
500g and each biscuit pack is 250g. What is the weight of all packs?
Key:3500g
7.6. There is 1879kg of rice to put into bags. Each bag can contain 8kg at
most. How many bags at least are needed?
Key:235
7.7. A man has 64 rabbits. After selling ¼ of the rabbits, he puts them
equally into 6 cages. How many rabbits in each cage?
Key: 8

7.8. In a running race, Manh ran in 3 minutes 16 seconds, Nam ran in 2
minutes 55 seconds and Toan ran in 3 minutes 5 seconds. How much
time did all 3 boys run in total?
Key: 9phút16giaay
7.9. 1/3 of a rice pack is 20kg. What is the weight of 5 packs of rice?
Key: 300