6 Ask Friend Think Four Digit Decimal Number Abcd Reverse Like Dcba Subtract One Taking Ab Q43878892
6. You ask your friend to think of a four-digit (decimal) number abcd, reverse it like dcba, and subtract the one from the other (taking the absolute value of the difference). Then you ask him/her to leave out one of the non-zero digits of the difference, and calculate the sum of the remaining digits (of the difference). When your friend tells you this sum, you should be able to figure out the digit that was left out. How? Hint: A (decimal) number is divisible by 9 if and only if the sum of its digits is divisible by 9. Show transcribed image text 6. You ask your friend to think of a four-digit (decimal) number abcd, reverse it like dcba, and subtract the one from the other (taking the absolute value of the difference). Then you ask him/her to leave out one of the non-zero digits of the difference, and calculate the sum of the remaining digits (of the difference). When your friend tells you this sum, you should be able to figure out the digit that was left out. How? Hint: A (decimal) number is divisible by 9 if and only if the sum of its digits is divisible by 9.
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Answer to 6. You ask your friend to think of a four-digit (decimal) number abcd, reverse it like dcba, and subtract the one from t…
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