The sum of two digits is 12 and the sum of their reciprocals is 4/9. Then find the larger of these digits.

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  1. 9
  2. 5
  3. 4
  4. 2

Answer (Detailed Solution Below)

Option 1 : 9
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UP Police SI (दरोगा) Official PYP (Held On: 2 Dec 2021 Shift 1)
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Detailed Solution

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Given:

Sum of two digits = 12

Sum of their reciprocals = 4/9

Formula Used:

Let the two digits be x and y.

x + y = 12

1/x + 1/y = 4/9

Calculation:

From the second condition:

⇒ (y + x) / (xy) = 4/9

Substitute x + y = 12:

⇒ 12 / (xy) = 4/9

⇒ xy = (12 × 9) / 4

⇒ xy = 108 / 4

⇒ xy = 27

Now we have two equations:

1) x + y = 12

2) xy = 27

We need to find two numbers whose sum is 12 and product is 27.

Consider the factors of 27: (1, 27), (3, 9).

The pair (3, 9) satisfies the condition x + y = 12 (3 + 9 = 12).

So, the two digits are 3 and 9.

The larger of the two digits is 9.

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