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A number which reads the same when read forward and backward is called a palindrome.
Q.How many four-digit numbers are palindromes?
  • a)
    81
  • b)
    90
  • c)
    99
  • d)
    100
  • e)
    115 
Correct answer is option 'B'. Can you explain this answer?
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Verified Answer
A number which reads the same when read forward and backward is called...
A 4-digit palindrome will be of the form abba where a > 0 and b can take integer values from 0 to 9.
a can take 9 values and b can take 10 values.
The total number of 4-digit palindromes is 9 x 10 = 90 Hence, option 2.
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Most Upvoted Answer
A number which reads the same when read forward and backward is called...
Understanding Four-Digit Palindromes
A four-digit palindrome takes the form of ABBA, where A and B are digits. The first half mirrors the second half, creating the palindrome effect.
Structure of a Four-Digit Palindrome
- First Digit (A):
- Must be a non-zero digit (1-9) to maintain the four-digit requirement.
- This gives us 9 possible choices (1 through 9).
- Second Digit (B):
- Can be any digit from 0 to 9.
- This provides 10 possible choices (0 through 9).
Calculating the Total
To find the total number of four-digit palindromes, we multiply the choices for A and B:
- Choices for A: 9
- Choices for B: 10
Thus, the total number of four-digit palindromes is calculated as follows:
- Total Palindromes = Choices for A × Choices for B
- Total Palindromes = 9 × 10 = 90
Conclusion
Therefore, the correct answer is option 'B', which is 90. This calculation illustrates how the structure of palindromes limits the possibilities based on the digits available.
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Group QuestionAnswer the following questions based on the information given below.A certain building built up in the rectangular shape contains 10 apartments numbered from 0 to 9. The area of each apartment is dependent on the floor on which it is situated. Further all the apartments on any floors are of same size. However the total area of all the apartments put together on each of the floor is equal. The top floor is considered as row 1 in this building.The apartments are however are not numbered in serial fashion. The clues below indicate the apartment numbers situated on any of the floors.1. The sum of four apartment numbers in 4th row is 28.2. The biggest apartment number in row 3 is in the central apartment of the floor.3. The 3rd apartment number from the left in the bottom row isnt 7.4. The sum of rightmost apartment numbers in the four rows put together is 11.5. The apartments numbered 0 and 5 are in different rows of this building.6. The number of the apartment at the top minus the number of leftmost apartment in row 2 is 4. 7. The sum of leftmost apartment numbers in the four rows sum to 20.Q.Which apartment number has the largest area? Correct answer is '6'. Can you explain this answer?

A certain building built up in the rectangular shape contains 10 apartments numbered from 0 to 9. The area of each apartment is dependent on the floor on which it is situated. Further all the apartments on any floors are of same size. However the total area of all the apartments put together on each of the floor is equal. The top floor is considered as row 1 in this building.The apartments are however are not numbered in serial fashion. The clues below indicate the apartment numbers situated on any of the floors.1. The sum of four apartment numbers in 4th row is 28.2. The biggest apartment number in row 3 is in the central apartment of the floor.3. The 3rd apartment number from the left in the bottom row isnt 7.4. The sum of rightmost apartment numbers in the four rows put together is 11.5. The apartments numbered 0 and 5 are in different rows of this building.6. The number of the apartment at the top minus the number of leftmost apartment in row 2 is 4. 7. The sum of leftmost apartment numbers in the four rows sum to 20.Q.Which row has the least sum of all the apartments? Correct answer is '2'. Can you explain this answer?

A certain building built up in the rectangular shape contains 10 apartments numbered from 0 to 9. The area of each apartment is dependent on the floor on which it is situated. Further all the apartments on any floors are of same size. However the total area of all the apartments put together on each of the floor is equal. The top floor is considered as row 1 in this building.The apartments are however are not numbered in serial fashion. The clues below indicate the apartment numbers situated on any of the floors.1. The sum of four apartment numbers in 4th row is 28.2. The biggest apartment number in row 3 is in the central apartment of the floor.3. The 3rd apartment number from the left in the bottom row isnt 7.4. The sum of rightmost apartment numbers in the four rows put together is 11.5. The apartments numbered 0 and 5 are in different rows of this building.6. The number of the apartment at the top minus the number of leftmost apartment in row 2 is 4. 7. The sum of leftmost apartment numbers in the four rows sum to 20.Q. What is the sum of the apartment numbers in the bottom row which are not at extreme ends? Correct answer is '15'. Can you explain this answer?

A certain building built up in the rectangular shape contains 10 apartments numbered from 0 to 9. The area of each apartment is dependent on the floor on which it is situated. Further all the apartments on any floors are of same size. However the total area of all the apartments put together on each of the floor is equal. The top floor is considered as row 1 in this building.The apartments are however are not numbered in serial fashion. The clues below indicate the apartment numbers situated on any of the floors.1. The sum of four apartment numbers in 4th row is 28.2. The biggest apartment number in row 3 is in the central apartment of the floor.3. The 3rd apartment number from the left in the bottom row isnt 7.4. The sum of rightmost apartment numbers in the four rows put together is 11.5. The apartments numbered 0 and 5 are in different rows of this building.6. The number of the apartment at the top minus the number of leftmost apartment in row 2 is 4. 7. The sum of leftmost apartment numbers in the four rows sum to 20.Q.f the rightmost apartment in the bottom row has the least area, which of the following apartment has the least area? Correct answer is '4'. Can you explain this answer?

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A number which reads the same when read forward and backward is called a palindrome.Q.How many four-digit numbers are palindromes?a)81b)90c)99d)100e)115Correct answer is option 'B'. Can you explain this answer?
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