ICSE Class 5 Mathematics · Chapter 1 · Number System

Chapter 1 Workbook — Number System

ICSE Class 5 Mathematics practice workbook: concepts, warm-up exercises and a complete answer key with explanations.

Why It Matters

Number System is the Foundation of Mathematics

It helps us to read, write, compare and understand numbers in our daily life — from bank accounts and prices to scores and vehicle numbers.

Natural Numbers (N): 1, 2, 3, 4, 5, ... (Counting numbers)
Whole Numbers (W): 0, 1, 2, 3, 4, 5, ... (Includes 0)
Integers (Z): ... −3, −2, −1, 0, 1, 2, 3, ... (Negative, zero and positive)
Even Numbers: Numbers divisible by 2 → 2, 4, 6, 8, ...
Odd Numbers: Numbers not divisible by 2 → 1, 3, 5, 7, ...
Place Value: Value of a digit based on its position. Example: 1,53,274 = 1,00,000 + 50,000 + 3,000 + 200 + 70 + 4
Practice

Chapter Exercises

A. Warm-Up! Fill in the Blanks

1. The smallest natural number is ______.

2. 0 is a ______ number but not a natural number.

3. The predecessor of 10 is ______.

4. The successor of 99,999 is ______.

5. 1,00,000 is written as ______ in the international system.

B. Multiple Choice Questions (MCQs)

1. Which of the following is a natural number?

A. 0B. −1C. 1D. 1/2

2. Which of the following is the smallest 6-digit number?

A. 99,999B. 1,00,000C. 9,999D. 10,000

3. The place value of 6 in 5,36,709 is

A. 60B. 600C. 6,000D. 60,000

4. Which of the following numbers is an odd number?

A. 246B. 864C. 315D. 420

5. How many zeros are there in one lakh?

A. 3B. 4C. 5D. 6

6. The expanded form of 7,83,205 is

A. 7,00,000+8,30,000+200+5B. 7,00,000+80,000+3,000+200+5C. 7,00,000+8,00,000+3,000+200+5D. 70,000+8,000+300+20+5

C. Fill in the Blanks

1. The number after 7,99,999 is ______.

2. 4,05,060 = ______ thousands ______ tens ______ ones.

3. The place value of 8 in 8,24,761 is ______.

4. The number 3,70,000 has ______ hundreds.

5. The greatest 5-digit number is ______.

D. True or False

1. Zero is a natural number. (   )

2. 999 comes after 1,000. (   )

3. 6,40,000 has 6 thousands. (   )

4. All even numbers end with 0, 2, 4, 6 or 8. (   )

5. 1,00,000 is greater than 99,999. (   )

E. Match the Following

Column A
1.2,45,678
2.9,09,090
3.5,07,300
4.1,23,004
5.7,80,050
Column B
a)Seven lakh eighty thousand fifty
b)Two lakh forty five thousand six hundred seventy eight
c)One lakh twenty three thousand four
d)Five lakh seven thousand three hundred
e)Nine lakh nine thousand ninety

F. Short Answer Type Questions

1. Write the place value and face value of 7 in 4,37,621.

2. Write the expanded form of 6,54,321.

3. Write the number name for 8,00,604.

4. Write the predecessor and successor of 5,00,000.

5. Write the smallest 5-digit number and the greatest 5-digit number.

G. Problem Solving

1. A school has 2,34,567 books in the library. If 45,678 more books are added, how many books are there in total?

2. In a city, the population is 7,85,432. If 1,25,680 are males, how many females are there?

3. A factory produced 6,75,230 toys in 2023 and 7,25,410 toys in 2024. Find the total number of toys produced in two years.

4. A number is formed by 5 in lakh place, 3 in thousand place, 2 in ten place and 8 in ones place. Write the number and its number name.

H. HOTS — Challenge Quest

1. Form the greatest and the smallest 6-digit numbers using the digits 7, 0, 3, 9, 1, 5 (each digit used once).

2. Can you find two different 6-digit numbers with the same digits whose sum is 10,00,000?

Check Your Work

Answer Key

Try every exercise first, then check your answers here.

A. Warm-Up 1. 1   2. whole   3. 9   4. 1,00,000   5. 100,000 (one hundred thousand)
B. MCQs 1. C   2. B   3. C   4. C   5. C   6. B
C. Fill in the Blanks 1. 8,00,000   2. 405 thousands 6 tens 0 ones   3. 8,00,000   4. 3,700   5. 99,999
D. True or False 1. False   2. False   3. False   4. True   5. True
E. Match 1-b   2-e   3-d   4-c   5-a
F. Short Answer 1. place value 7,000; face value 7   2. 6,00,000 + 50,000 + 4,000 + 300 + 20 + 1   3. Eight lakh six hundred four   4. predecessor 4,99,999; successor 5,00,001   5. 10,000 and 99,999
G. Problem Solving 1. 2,80,245 books   2. 6,59,752 females   3. 14,00,640 toys   4. 5,03,028 — five lakh three thousand twenty-eight
H. HOTS 1. greatest 9,75,310; smallest 1,03,579   2. e.g. 1,08,950 + 8,91,050 = 10,00,000 (many other pairs work)
Worth a second look
B.2 — 99,999 has only 5 digits, so the smallest 6-digit number is 1,00,000. B.5 — 1,00,000 = 1 followed by five zeros.
C.2 — 4,05,060 = 405 × 1,000 + 6 × 10, so 405 thousands, 6 tens, 0 ones. C.4 — 3,70,000 ÷ 100 = 3,700 hundreds.
D.3 — 6,40,000 is 640 thousands (6 is in the lakh place, not the thousands place).
G.1–G.3 — add or subtract place by place, carrying/borrowing as needed: 2,34,567 + 45,678 = 2,80,245; 7,85,432 − 1,25,680 = 6,59,752; 6,75,230 + 7,25,410 = 14,00,640.
H.1 — the greatest number uses the digits in descending order; for the smallest, 0 cannot go first (that would make a 5-digit number), so start with 1 and then use 0, 3, 5, 7, 9.
H.2 — in 1,08,950 + 8,91,050 the ones add to 0, the tens add to 10 (5 + 5), and every other pair of digits adds to 9 (1 + 8, 0 + 9, 8 + 1, 9 + 0). With the carry each column becomes 10, so the total is 10,00,000. Both numbers use the digits 0, 0, 1, 5, 8, 9.