The ratio between a two digit number and the number obtained by reversing its digits is 4 ∶ 7. What is the sum of all such possible pairs of numbers?

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OSSC Soil Conservation Extension Worker Official Paper II (Held on 22nd Oct 2017)
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  1. 99
  2. 120
  3. 132
  4. 210
  5. 330

Answer (Detailed Solution Below)

Option 5 : 330

Detailed Solution

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Given:

The ratio between a two digit number and the number obtained by reversing its digits is 4 : 7.

Calculation:

Let the two-digit number be 10a + b and the number obtained by reversing its digit be 10b + a

⇒ (10a + b)/(10b + a) = 4/7

⇒ 70a + 7b = 40b + 4a

⇒ 66a = 33b

⇒ a/b = 1/2

possible two digit pairs are (12, 21), (24, 42), (36, 63), (48, 84)

sum of all such possible pairs = (12 + 21 + 24 + 42 + 36 + 63 + 48 + 84) = 330

∴ the correct answer is 330.

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