document.write( "Question 1161125: A bag contains 4 red marbles, 3 green ones, 1 lavender one, 3 yellows, and 2 orange marbles.\r
\n" ); document.write( "\n" ); document.write( "How many sets of five marbles include at least three red ones?
\n" ); document.write( "

Algebra.Com's Answer #784596 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "\"At least 3\" means \"3 or more\". Considering there are 4 red marbles, the only possible scenarios are:
\n" ); document.write( "
  • picking exactly 3 red marbles
  • picking exactly 4 red marbles

\n" ); document.write( "--------------------------------------------\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Let's consider the situation where we have exactly 3 red marbles selected. There are 4 red marbles overall, which means there are 4 ways to form a group of 3 selected red. Put another way, there are 4 ways to not a select a particular red marble. \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Using the combination function, you should find that when n = 4 and r = 3.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "There are 3 green marbles, 1 lavender, 3 yellows and 2 orange giving a total of 3+1+3+2 = 9 marbles that aren't red. Use the combination function to find when n = 9 and r = 2. This says there are 36 ways to select two marbles from a pool of 9.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Multiply this with the number of ways to pick the red marbles (4) and we get 36*4 = 144\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "There are 144 ways to pick exactly 3 red marbles and 2 non-red marbles.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Let A = 144. We'll use it later.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "--------------------------------------------\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "We have 4 red marbles. There is only one way to select a group of 4 red marbles if the pool size is also 4. \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "There are 9 non-red marbles and only one slot to fill with this pool to pick from. So we have 9 different ways to fill it.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Overall, there are 1*9 = 9 different ways to pick four red marbles followed by one non-red marble.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Let B = 9\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "--------------------------------------------\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "The results from the earlier sections are then added up. The values of A and B can be added because the events they represent are mutually exclusive.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "A+B = 144+9 = 153\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Answer: 153
\n" ); document.write( "
\n" ); document.write( "
\n" );