document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1205180>Question 1205180</A>: <I><SPAN STYLE=\"word-break: break-all;\"> What's the total of one, two, three-digit prime numbers that can be formed using the digits 2, 3, 5 and 7. No digit can be used more than once in a number. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #841825 by </B><A HREF=/tutors/aboutme.mpl?userid=greenestamps><B>greenestamps(13203)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=greenestamps><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=greenestamps><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=841825\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "1-digit numbers....<BR>\n" );
document.write( "2, 3, 5, and 7 are all prime numbers.<BR>\n" );
document.write( "ANSWERS: 2, 3, 5, 7<br><BR>\n" );
document.write( "2-digit numbers....<BR>\n" );
document.write( "A 2-digit number is not prime if the last digit is 2 or 5, so the last digit has to be 3 or 7.<BR>\n" );
document.write( "The possibilities are 23, 27, 53, and 57.<BR>\n" );
document.write( "27 and 57 are not prime because their digit sum is divisible by 3.<BR>\n" );
document.write( "23 and 53 are both prime, by inspection<BR>\n" );
document.write( "ANSWERS: 23, 53<br><BR>\n" );
document.write( "3-digit numbers....<BR>\n" );
document.write( "Again the last digit can't be 2 or 5; it has to be 3 or 7.<BR>\n" );
document.write( "The 3-digit combinations 2,3,7 and 3,5,7 won't work because the digit sum is divisible by 3.<BR>\n" );
document.write( "The other 3-digit combinations are 2,3,5 and 2,5,7; in each of those combinations neither the 2 nor the 5 can be the last digit, so the possible prime numbers are 253, 523, 257, and 527.<br><BR>\n" );
document.write( "Assuming we aren't working the problem simply by checking a list of prime numbers, here we have some actual detective work to do to see which if any of these are prime numbers.<br><BR>\n" );
document.write( "I won't go into details (I leave that for the student); the prime numbers among these are 523 and 257.<br><BR>\n" );
document.write( "ANSWERS: 257, 523<br><BR>\n" );
document.write( "Final list of 1-, 2-, or 3-digit prime numbers using digits 2, 3, 5, and 7 without repetition:<br><BR>\n" );
document.write( "2, 3, 5, 7, 23, 53, 257, 523<br><BR>\n" );
document.write( "Since \"total\" is not a formal mathematical term, I won't guess what the expected answer is to the given problem.  The student can use this list to answer the question, based on his/her interpretation.<br><BR>\n" );
document.write( " </SPAN>\n" );
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