Discussion :: Problems on Numbers
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The difference between the digits of a two-digit number is 4. What is the digit in the unit's place? To find out the answer, which of the information given in the statements P and Q is/are sufficient?
P: The difference between the number and the number obtained by interchanging the positions of the digits is 36.
Q: The sum of the digits of that number is 12.
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A.
Only P is sufficient
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B.
Only Q is sufficient
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C.
Both P and Q are needed
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D.
Either P or Q is sufficient.
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Answer : Option B
Explanation :
Let the ten's digit be x and the unit's digit be (x - 4).
P gives: [10x + (x-4)] - [10(x-4) + x] = 36
This does not give the value of x.
∴Unit's place digit cannot be found.
Q gives: x + x - 4 = 12
2x = 12 + 4
2x = 16
X = 8
Hence, unit's digit: X - 4 = 8 - 4 = 4.
So, only Q is sufficient.
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