document.write( "Question 785651: How many ways can 5 different books be arranged if one book cannot be at either ends?? \n" ); document.write( "

Algebra.Com's Answer #477659 by xinxin(76) $\"\"$ $\"About$

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Draw 5 slots:
\n" ); document.write( "___ ___ ___ ___ ___
\n" ); document.write( "Since one book should be in the middle slots, we will get 3 situations:
\n" ); document.write( "(1)_4_ _1_ _3_ _2_ _1_
\n" ); document.write( "(2)_4_ _3_ _1_ _2_ _1_
\n" ); document.write( "(3)_4_ _3_ _2_ _1_ _1_
\n" ); document.write( "* The numbers (4,3,2,1) indicate the number of books can be put in the slot.
\n" ); document.write( "Th answer is 4*3*2*1*1 + 4*3*1*2*1 + 4*3*2*1*1 = 72\r
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