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The sum of the digits of a two digit number is six. Interchange the digits and the new number is 18 less than the old number. What is the number?
Analysis: This problem requires two tables - one for the old number and one for the new number. The tables' rows are labeled with the formula for a number in the decimal system: number = tens digit X 10 + units digit. The number formula gives:old number = old tens weight X tens unknown + old units weight X units unknown new number = new tens weight X tens unknown + new units weight X units unknownThe numbers represented by the two tables are related by 18, i.e. old number = new number + 18 and the first sentence in the problem tells us that old units unknown + old tems unknown = 6. This provides two equations in two unknows. Simultaneously solving the equations gives the program. Click to see the digit table, the program (an expand program display), or the results.