document.write( "Question 658824: five bulbs of which three are defective are to be tried in two bulb points in a dark room. number of trials the room shall be lighted is? answer is 7 pls solve this thank u \n" ); document.write( "
Algebra.Com's Answer #410483 by Theo(13342)\"\" \"About 
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5 bulbs
\n" ); document.write( "3 defective
\n" ); document.write( "2 good
\n" ); document.write( "2 bulbs placed in a room.
\n" ); document.write( "how many trials required to get the room to light.
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\n" ); document.write( "you only need 1 good bulb to light the room.
\n" ); document.write( "the number of possible combinations would be C(5,2) which is equal to 10 possible combinations.
\n" ); document.write( "the number of possible combinations of 2 that would involve only defective bulbs would be C(3,2) which is equal to 3.
\n" ); document.write( "10 - 3 leaves 7 combinations where the room will be lighted.
\n" ); document.write( "let's see if this works out.
\n" ); document.write( "let d1, d2, d3 represent the defective bulbs.
\n" ); document.write( "let g1, g2 represent the good bulbs.
\n" ); document.write( "the total possible combinations are:
\n" ); document.write( "d1, d2 = room is dark *****
\n" ); document.write( "d1, d3 = room is dark *****
\n" ); document.write( "d1, g1 = room is light
\n" ); document.write( "d1, g2 = room is light
\n" ); document.write( "d2, d3 = room is dark *****
\n" ); document.write( "d2, g1 = room is light
\n" ); document.write( "d2, g2 = room is light
\n" ); document.write( "d3, g1 = room is light
\n" ); document.write( "d3, g2 = room is light
\n" ); document.write( "g1, g2 = room is light
\n" ); document.write( "there are 3 possible situations where the room will still be dark.
\n" ); document.write( "there are 7 possible situations where the room will be light.\r
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