document.write( "Question 636339: 7. A sample of 320 mobile phone batteries contained 16 defective batteries. How many defective batteries would you expect to find in a sample of 3000?\r
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Algebra.Com's Answer #400933 by math-vortex(648) $\"\"$ $\"About$

You can put this solution on YOUR website!

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document.write( "Hi, there--\r\n" );
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document.write( "The problem:\r\n" );
document.write( "A sample of 320 mobile phone batteries contained 16 defective batteries. How many defective\r\n" );
document.write( "batteries would you expect to find in a sample of 3000?\r\n" );
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document.write( "A solution:\r\n" );
document.write( "You can use proportional reasoning to solve this problem. Let x be the number of defective\r\n" );
document.write( "batteries in the larger sample.\r\n" );
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document.write( " THere are several different ways to set up a proportion for this problem. Just remember to \r\n" );
document.write( "match your units. I like to say the proportion out loud. This keeps me from getting the \r\n" );
document.write( "proportion upside down. Here is one possible proportion:\r\n" );
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document.write( "[number of DEFECTIVES in SMALLER sample] over [number of BATTERIES in SMALLER sample] \r\n" );
document.write( "equals [number of DEFECTIVES in LARGER sample] over [number of BATTERIES in LARGER \r\n" );
document.write( "sample]\r\n" );
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document.write( "Now we substitute in the known values and variable.\r\n" );
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document.write( "Solve for x.\r\n" );
document.write( "We can cross-multiply here. (NOTE: many teachers frown on the cross-multiply technique. \r\n" );
document.write( "If your teacher is one of those, see an alternate method below.)\r\n" );
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document.write( "We would expect to find 150 defective batteries in the larger sample.\r\n" );
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document.write( "SOLUTION METHOD WITHOUT CROSS_MULTIPLYING\r\n" );
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document.write( "Multiply both sides of the equation by 3000 to isolate the variable on the right side.\r\n" );
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document.write( "Simplify left side using multiplication and division.\r\n" );
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document.write( "We have the same answer, 150 defective batteries in the larger sample.\r\n" );
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document.write( "Feel free to email if you have questions about this.\r\n" );
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document.write( "Ms.Figge\r\n" );
document.write( "math.in.the.vortex@gmail.com\r\n" );
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