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The addition of a three-digit number and the number with the same digits in reverse order, is 1089. The middle digit of that number must be
Question

The addition of a three-digit number and the number with the same digits in reverse order, is 1089. The middle digit of that number must be

A.

9

B.

8

C.

0

D.

4

Correct option is A

Solution:

Step 1: Define the Number

Let the three-digit number be represented as xyz, where:

  • x is the hundreds digit,
  • y is the tens digit,
  • z is the units digit.

The number in numeric form is: 100x + 10y + z.

The reverse of the number is: 100z + 10y + x.

According to the problem: (100x + 10y + z) + (100z + 10y + x) = 1089.

Step 2: Simplify the Equation

Expanding the sum: 100x + 10y + z + 100z + 10y + x = 1089.

Combining like terms: (100x + x) + (100z + z) + (10y + 10y) = 1089.

This simplifies to: 101x + 101z + 20y = 1089.

Factoring out 101 from the first two terms: 101(x + z) + 20y = 1089.

Step 3: Solve for x + z

Since 101(x + z) must be a multiple of 101, dividing 1089 by 101 gives:

1089 ÷ 101 = 10.79.

Since this is not an integer, we check integer values for x + z that make the sum a multiple of 101.
From estimation: x + z = 9.

Now, substituting x + z = 9 into the equation:

101(9) + 20y = 1089.

909 + 20y = 1089.

20y = 180.

y = 9.

Step 4: Verify the Answer

  • The middle digit of the number is y.
  • We found y = 9.

Thus, the correct answer is:

Final Answer: (a) 9

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