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16 Sep 2014, 00:43
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If \(x\) is a three-digit positive integer, what is the value of its tens digit?
(1) The tens digit of \((x + 8)\) is 5.
(2) The units digit of \((x + 9)\) is 7.
(1) The tens digit of \((x + 8)\) is 5.
(2) The units digit of \((x + 9)\) is 7.
16 Sep 2014, 00:43
Kudos
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Official Solution:
If \(x\) is a three-digit positive integer, what is the value of its tens digit?
(1) The tens digit of \((x + 8)\) is 5.
If \(x=149\), the tens digit of \(x\) is 4. However, if \(x = 150\), the tens digit of \(x\) is 5. Not sufficient.
(2) The units digit of \((x + 9)\) is 7.
From this, we can infer that the units digit of \(x\) is 8, but this alone does not determine the tens digit. Not sufficient.
(1)+(2) Knowing the units digit of \(x\) is 8 implies there will be a carry-over from the units to the tens place in \((x + 8)\), making its tens digit one more than the tens digit of \(x\). Thus, the tens digit of \(x\) is 4. Sufficient.
Answer: C
If \(x\) is a three-digit positive integer, what is the value of its tens digit?
(1) The tens digit of \((x + 8)\) is 5.
If \(x=149\), the tens digit of \(x\) is 4. However, if \(x = 150\), the tens digit of \(x\) is 5. Not sufficient.
(2) The units digit of \((x + 9)\) is 7.
From this, we can infer that the units digit of \(x\) is 8, but this alone does not determine the tens digit. Not sufficient.
(1)+(2) Knowing the units digit of \(x\) is 8 implies there will be a carry-over from the units to the tens place in \((x + 8)\), making its tens digit one more than the tens digit of \(x\). Thus, the tens digit of \(x\) is 4. Sufficient.
Answer: C
12 Mar 2015, 15:28
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Can you explain how tens digit of X + 8 = 5, gives us two options 4 and 5. I would think it should be 6 and 7
