Reversing a two-digit number decreases its value by 45. If the digits of the new number sum to 13, what was the original number?
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Answer: B. 94
Explanation
A two digit number is represented algebraically by tens and units place value components. Reversing the digits changes the value, and the difference is given as forty five. Testing candidate numbers confirms that ninety four satisfies both the reversal and digit sum rules. Two digit numbers are expressed mathematically as ten times the tens digit plus the units digit. Reversing a number swaps the positions of its tens and units place values. Digit sum problems test understanding of positional number systems in base ten arithmetic.
Positional number systems are fundamental in computer science and digital data representation. Reversal puzzles help students grasp the underlying structure of base ten arithmetic numbers. Cryptarithms and number puzzles are classic exercises in deductive mathematical logic. Option a gives forty nine which increases rather than decreases when its digits are reversed. Option c suggests eighty three whose digit sum and reversal difference do not match the prompt. Option d is incorrect because a single definite two digit number satisfies all conditions.
- Subject
- Mathematics
- Category
- Mathematics
- Topic
- —
- Difficulty
- medium
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