Q1: How many four digit numbers are there in all?
Ans: We know that the 10 digits are 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9
0 cannot be used in thousands place so only nine digits can be used.
10 digits can be used in hundreds, tens and units place
The number of four digit numbers = 9 × 10 × 10 × 10 = 9000
Therefore, 9000 four digit numbers are there in all.
Q2: Write the smallest and the largest six digit numbers. How many numbers are between these two.
Ans: We know that the smallest digit is 0 which cannot be used in the highest place value.
So 1 which is the second smallest digit can be used in the highest place value
The required smallest six digit number is 100000
We know that the largest digit is 9 which can be used in any place
The required largest six digit number is 999999
So we get the difference = 999999 – 100000 = 899999
Therefore, the smallest six digit number is 100000, the largest six digit number is 999999 and 899999 numbers are between these two numbers.
Q3: How many 8digit numbers are there in all?
Ans: We know that the 10 digits are 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9
0 cannot be used in the highest place value and 9 can be used in the highest place value
So the 10 digits can be used in the remaining places of 8 digit numbers
The total number of 8 digit numbers = 9 × 10 × 10 × 10 × 10 × 10 × 10 × 10 = 90000000
Therefore, 90000000 eight digit numbers are there in all.
Q4: Write 10075302 in words and rearrange the digits to get the smallest and the largest numbers.
Ans: The given number 10075302 can be written as one crore seventy five thousand three hundred and two.
To get smallest 8 digit number using 0, 1, 2, 3, 5 and 7
We use 1 which is the smallest digit in the highest place and largest digit 7 at the units place
Further we put 5 in the tens place, 3 in the hundreds place and 2 in thousands place
So the required smallest number is 10002357
To get largest 8 digit number using 0, 1, 2, 3, 5 and 7
We use 7 which is the largest digit in the highest place value, 5 in a place after highest place, 3 as the next one, 2 as the smallest digit and then 1.
So the required largest number is 75321000.
Q5: What is the smallest 3digit number with unique digits?
Ans: 102 is the smallest 3digit number with unique digits.
Q6: What is the largest 5digit number with unique digits?
Ans: 98765 is the largest 5digit number with unique digits.
Q7: Write the smallest 3digit number which does not change if the digits are in reverse order.
Ans: 101 is the smallest 3digit number which does not change if the digits are in reverse order.
Q8: Find the difference between the number 279 and that obtained on reversing its digits.
Ans: The reverse of 279 is 972
Difference between both the numbers = 972 – 279 = 693
Therefore, the difference between the number 279 and that obtained on reversing its digits is 693.
Q9: Form the largest and smallest 4digit numbers using each of digits 7, 1, 0, 5 only once.
Ans: The largest 4 digit number = 7510
Smallest 4 digit number = 1057
Therefore, the largest and smallest 4digit numbers using each of digits 7, 1, 0, 5 only once is 7510 and 1057.
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1. What is the importance of knowing our numbers in mathematics? 
2. How can knowing our numbers help in reallife situations? 
3. What are the different types of numbers that we should be familiar with? 
4. Why is it important to understand place value when dealing with numbers? 
5. How can knowing our numbers help improve our problemsolving skills? 

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