Sage B.

asked • 08/07/19

Combinations and Permutations

I understand that most combination word problems use words such as “and” (which means to multiply) and some use the word “or” (which means to add).


However, are there any instances where a combination or permutations math question can include both “and” and “or”? If so, how do you go about solving those kinds of problems?


For instance, with combo #1 you can get sides A and B, with combo #2 you can get sides C and D, with combo #3 you can get sides E and F. All combos come with a beverage choice of water, milk, or lemonade. How many combinations can be made?

2 Answers By Expert Tutors

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Sage B.

Thanks Jim! Would the answer be the same if the problem was worded with “or” instead of “and”? For example, with combo #1 you can get sides A OR B, with combo #2 you can get sides C OR D, with combo #3 you can get sides E OR F. All combos come with a beverage choice of water, milk, or lemonade. How many combinations can be made?
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08/08/19

Jim S.

tutor
Sage, I see now what concerns you. The concept has to do with categories being mutual exclusive. The problem I solved assumed all were mutually exclusive (or). But if you get sides A & B with combo #1 that is only counted as one meal not 2. So you only have 1 # and 1#2 and 1#3 so that is 3 different combos and 3 mutually exclusive drink choices which gives us 9 (3 different meals and 3 different drinks) different combinations. Hope this helps clear up the confusion. Jim
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08/08/19

Nestor R. answered • 08/07/19

Tutor
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Professional experienced using mathematics and statistics

Sage B.

Thanks! One more question. How would the answer change if the problem stated a combo can only come with a choose of one of one of the sides. For instance, with combo #1 you can choose from sides A OR B, with combo #2 you can get sides C OR D, with combo #3 you can get sides E OR F. All combos come with a beverage choice of water, milk, or lemonade. How many combinations can be made?
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08/07/19

Nestor R.

In this case each combo has 2 possibilities and each of those possibilities has the option of one of 3 drinks. There are 3 combos, with 2 choices of side per combo and 3 choices of drink, so the answer becomes 3 x 2 x 3 = 18 possible combinations.
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08/08/19

Sage B.

Thanks so much! I’ve seen questions like this on the teacher certification (EC-6 Math) and could not figure out how to approach these questions. I’ve been told to use the combination formula nCr=n!/r!(n-r)!
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08/08/19

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