CBSE SOLUTIONS-2026-27
CLASS-7
CHAPTER-1 NUMBER SYSTEM
A. Multiple Choice Questions:
Q1. The number system consists of 0 and 1 is known as:
(A) Binary number system
(B) Decimal number system
(C) Octal number system
(D) Hexadecimal number system
Answer: (A) Binary number system
Q2. The number system having ‘10’ as its base:
(A) Binary number system
(B) Decimal number system
(C) Octal number system
(D) Hexadecimal number system
Answer: (B) Decimal number system
Q3. The number system having ‘16’ as its base:
(A) Binary number system
(B) Decimal number system
(C) Octal number system
(D) Hexadecimal number system
Answer: (D) Hexadecimal number system
Q4. In hexadecimal number system, a stands for:
(A) 10
(B) 11
(C) 12
(D) None of these
Answer: (A) 10
Q5. This number system consists of eight digits:
(A) Binary number system
(B) Decimal number system
(C) Octal number system
(D) Hexadecimal number system
Answer: (C) Octal number system
B. Write TRUE or FALSE:
Q1. Binary number system is used by all digital computers to convert the data input by you into its binary equivalent.
Answer: TRUE
Q2. The octal number system uses sixteen digits, having the base 16.
Answer: FALSE
Q3. Computers operate using binary code that consists of 0s and 1s.
Answer: TRUE
Q4. Hexadecimal is widely used in computing and digital electronics.
Answer: TRUE
Q5. The base of decimal number system is 10.
Answer: TRUE
C. Fill in the blanks with the words given below:
(hexadecimal, octal, subtraction, binary, data)
Q1. Since, _______________ number system uses two digits, it has base 2.
Answer: binary
Q2. Just like in decimal _______________ , when the top digit is smaller, we borrow from the next left digit.
Answer: subtraction
Q3. The _______________ given by the user is converted into binary code for processing.
Answer: data
Q4. The base of _______________ number system is 16.
Answer: hexadecimal
Q5. 8 is the base of _______________ number system.
Answer: octal
D. Answer these questions:
Q1. Explain the number system. Name the different types of number systems.
Answer:
A number system is a method to represent numbers using digits and a base value.
Different types of number systems are:
* Binary (Base 2)
* Decimal (Base 10)
* Octal (Base 8)
* Hexadecimal (Base 16)
Q2. Briefly explain the binary number system.
Answer:
The binary number system is a base-2 system that uses only two digits: 0 and 1. It is the fundamental language of computers because electronic circuits work on two states (ON = 1, OFF = 0). All data in computers is stored and processed in binary form.
Q3. What is hexadecimal number system?
Answer:
Hexadecimal is a base-16 number system. It uses 16 symbols: digits 0 to 9 and letters A to F (where A = 10, B = 11, C = 12, D = 13, E = 14, F = 15). It is commonly used in computing because it is short and easy to convert to binary (1 hex digit = 4 binary digits).
Q4. Write the rules for adding two binary numbers.
Answer:
Rules for binary addition:
1. 0 + 0 = 0
2. 0 + 1 = 1
3. 1 + 0 = 1
4. 1 + 1 = 10 (write 0, carry 1)
Q5. What are the rules for converting a decimal number into an octal number?
Answer:
To convert decimal to octal:
1. Divide the decimal number by 8 repeatedly.
2. Keep writing the remainders.
3. Stop when the quotient becomes 0.
4. Read the remainders from bottom to top.
Q6. Write the rules for subtracting two binary numbers.
Answer:
Rules for binary subtraction:
1. 0 – 0 = 0
2. 1 – 0 = 1
3. 1 – 1 = 0
4. 0 – 1 = 1 (borrow 1 from the next higher digit; the current digit becomes 2 – 1 = 1)
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