Question 931278
What is the 4 digit number... 
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...in which the first digit is one fifth of the last,... 
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That narrows it down to 

1--5
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...and the second and third digits are the last digit multiplied by 3?... 
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The last digit is 5, multiplied by 3 is 15, so 15 goes in the middle,
so the number is

1155
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The sum of the digits is 12
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That checks:  1+1+5+5=12.

Answer: 1155

Edwin</pre>