document.write( "Question 1202917: Peter the postman was managing some letters. After mailing out 4/5 of his letters, he received 30 new ones. He then mailed out 1/6 of his letters and received 15 more letters. In the end, Peter had 70 letters.
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Algebra.Com's Answer #838154 by ikleyn(52915)\"\" \"About 
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\n" ); document.write( "Peter the postman was managing some letters. After mailing out 4/5 of his letters,
\n" ); document.write( "he received 30 new ones. He then mailed out 1/6 of his letters and received 15 more letters.
\n" ); document.write( "In the end, Peter had 70 letters.
\n" ); document.write( "How many letters did he have at first?
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\n" ); document.write( "\n" ); document.write( "        This problem can be solved mentally,  by using the backward method.\r
\n" ); document.write( "\n" ); document.write( "        The solution is accessible for a  4th - 5th grade students  that are\r
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document.write( "In order for the solution be clear, I present the given part in steps.\r\n" );
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document.write( "    1.  First, he mailed out 4/5 of the letters.\r\n" );
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document.write( "    2.  Then 30 new letters arrived.\r\n" );
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document.write( "    3.  Then mailed out 1/6 of his letters.\r\n" );
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document.write( "    4.  Then 15 more letters arrived.\r\n" );
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document.write( "    5.  At the end, were there 70 letters.\r\n" );
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document.write( "Solving backward, we see that immediately before step 4, were there 70-15 = 55 letters.\r\n" );
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document.write( "These 55 letters comprised 5/6 of what he had immediately before step 3.\r\n" );
document.write( "Hence, 1/6 comprised 55/5 = 11 letter;  hence, immediately before step 3, there were 11*6 = 66 letters.\r\n" );
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document.write( "Hence, immediately before step 2, there were 66 - 30 = 36 letters.\r\n" );
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document.write( "These 36 letters comprised 1/5 of what he had at first.\r\n" );
document.write( "Hence, at first, there there 36*5 = 180 letters.\r\n" );
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\n" ); document.write( "\n" ); document.write( "To see many other similar  (and different)  solved problems by the backward method,  look into the lessons\r
\n" ); document.write( "\n" ); document.write( "    - Solving problems by the backward method \r
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\n" ); document.write( "\n" ); document.write( "Consider these lessons as your textbook,  handbook,  tutorials and free of charge home teacher,  which is always with you.\r
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