CLASS  VIILesson: 1. Number System (Solution)
1. Tick the correct option.
a. In the binary number system, right most digit before the fractional point is called
CROSS
2 (101)2 = 5
4 (100101101)2 = 301
6 (1100)2 = 12
8 (165)10 = 10100101
9 (1010001)2 = 81
10(1101010)2 = 106
TECH PRACTICE
1. (10111.011)2 = 23.375
2. (100110)2 – (1101)2 = 11001
3. Add the following binary number
a. 1000 + 101 = 1101
b. 1011 + 101 = 10000
c. 1001 + 101 = 1110
d. 1111 + 1111 = 11110
e. 11001 + 10101 = 101110
4. Convert the following decimal numbers into binary:
a. (19)10 = (10011)2
b. (98)10 = (1100010)2
c. (75)10 = (1001011)2
d. (37)10 = (100101)2
e. (54)10 = (110110)2
Touchpad Plus Class 7, Lesson 2
 MSD
 LSD
 BSD
 None of These
Answer: LSD
b. Base 2 is another name for the ________
 Binary number system
 Hexadecimal number system
 Decimal number system
 Octal number system
Answer: Binary Number System
c. _______ are the two symbols present in the binary number system.
 1 and 2
 0 and 1
 8 and 9
 5 and 6
Answer :0 and 1
d. The decimal number (345)_{10} is equivalent to _________
 (101011001)_{2}
 (110111001)_{2}
 (111011101)_{2}
 (111110001)_{2}
Answer: (101011001)_{2}
e. In binary addition, 0 + 1 is equal to
e. In binary addition, 0 + 1 is equal to
 0
 1
 10
 2
Answer: 1
2. Write 'T' for True and 'F' for False.
a. A number system is simply a manner of counting. True
b. The base of decimal number system is 8. False
c. The Word binary comes from 'Bi' meaning two. True
d. The octal number system is used as a shorthand representation of long binary numbers. True
e. The hexadecimal number system consists of 16 digits. True
a. In binary subtraction, 1 1 equal to 0
b. The base of Binary number system is 2
3. Fill in the blanks using the words from the help box.
binary, 0, 2, 8, 10, decimal number

a. In binary subtraction, 1 1 equal to 0
b. The base of Binary number system is 2
c. The base of decimal number system is 10.
d. In binary addition, 1 + 1 is equal to 10.
e. The o9ctal number system consists of 8 digits.
f. Computer system understands binary numbers.
b. How many bits are there in 1 nibble?
Answer: There are 4 bits in a nibble.
c. What do you mean by base in a number system?
Answer: The total number of digits used in a number system is called its base. It is also called radix.
Answer: A number system is a simply a method of counting. Computer also has its own number system, known as the binary number system.
b. What are the rules to convert a decimal number into a binary number?
Answer: We can convert the decimal number into binary number following given steps:
Step 1 Divide the decimal number by 2
Step 2 Note down the quotient and the reminder.
Step 3 Divide the quotient obtained again by 2 and note down the resulting quotient and reminder.
Step 4 Repeat the procedure till we reach a quotient less than 2.
Step 5 List the quotient and all the reminders.
c. Write the rules to subtract two binary numbers.
Answer: We can subtract binary number following the given rules in the box:
1 (10101)2 = 21
3 (1111011)2 = 123
5 (361)10 = 101101001
7 (6)10 = 110
4. Short answer type questions:
a. What is an octal number system?
Answer: The octal number system consists of eight digits from 0 to 7. Hence, the base of octal number system is 8 b. How many bits are there in 1 nibble?
Answer: There are 4 bits in a nibble.
c. What do you mean by base in a number system?
Answer: The total number of digits used in a number system is called its base. It is also called radix.
5. Long answer type questions:
a. What is number system? Explain?Answer: A number system is a simply a method of counting. Computer also has its own number system, known as the binary number system.
b. What are the rules to convert a decimal number into a binary number?
Answer: We can convert the decimal number into binary number following given steps:
Step 1 Divide the decimal number by 2
Step 2 Note down the quotient and the reminder.
Step 3 Divide the quotient obtained again by 2 and note down the resulting quotient and reminder.
Step 4 Repeat the procedure till we reach a quotient less than 2.
Step 5 List the quotient and all the reminders.
c. Write the rules to subtract two binary numbers.
Answer: We can subtract binary number following the given rules in the box:
X

Y

X  Y

0

0

0  0 = 0

0

1

0  1 =1
(Burrow 1, l So that 10  1 = 1)

1

0

1  0 = 1

1

1

1  1 = 0

FUN ZONE
Solve the crossword by filling it with equivalent decimal number or binary number.
DOWN1 (10101)2 = 21
3 (1111011)2 = 123
5 (361)10 = 101101001
7 (6)10 = 110
CROSS
2 (101)2 = 5
4 (100101101)2 = 301
6 (1100)2 = 12
8 (165)10 = 10100101
9 (1010001)2 = 81
10(1101010)2 = 106
TECH PRACTICE
1. (10111.011)2 = 23.375
2. (100110)2 – (1101)2 = 11001
3. Add the following binary number
a. 1000 + 101 = 1101
b. 1011 + 101 = 10000
c. 1001 + 101 = 1110
d. 1111 + 1111 = 11110
e. 11001 + 10101 = 101110
4. Convert the following decimal numbers into binary:
a. (19)10 = (10011)2
b. (98)10 = (1100010)2
c. (75)10 = (1001011)2
d. (37)10 = (100101)2
e. (54)10 = (110110)2
Touchpad Plus Class 7, Lesson 2
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