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| Math Central | Quandaries & Queries |
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Question from Nick: A sequence of 10 buttons can be arranged in a line. The buttons are identical except for colour, with each button being either red, blue or green. How many sequences can be made where there are exactly 2 red buttons as part of the sequence of 10 buttons? How many sequences can be made where there are exactly 4 red buttons as part of the sequence of 10 buttons? |
Hi Nick,
You have 10 positions in a line and you are to fill them according to the instructions given. I would choose 2 of the 10 positions for the placement of the red buttons. How many ways are there to choose 2 positions from 10?
You have now 8 unfilled positions and for each position you have 2 choices, blue or green. How many ways can you fill the 8 empty positions with either a blue or green button? For the problem in the link there are 8 possibilities for each position and you only have 2.
Write back if you need more assistance
Penny
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