why does he add one
Look at the Note below the question, it says “every set is a subset of itself”. Meaning set {4,19,1,6} is a subset of {4,19,1,6}. Let me put it this way
no. of sets with 1 element like {4}, {19},… = 4
no of sets with 2 elements like {4, 19}, {19, 6}… = 6
no of sets with 3 elements like {4, 19, 1}… = 4
no of sets with 4 elements {4,19,1,6} = 1. Total = 15
i thought the same but a really got hung up on the phrase every set is a subset of it self i thought that no. of set with 2 elements can be {4,19} and {19,4} so it would be 12 and so on.
what made you determine it wouldn’t be that case that i mentioned above
A set is nothing but a collection of numbers. So, {4,19} and {19,4} are essentially the same sets as the order of the numbers doesn’t matter. I hope, this helped you.
ok so the rule of thumb should be a set cannot have repeats and the order of numbers in any set dose not matter is that right
Not exactly, a set can have repeated elements eg: {1,2,2,2,3}, but it is no different from {2,1,2,3,2}. They are both same, and it is in the context the order doesn’t matter. If you have to calculate mean, median and mode for the values in the set, you must arrange them in ascending order.
a set cannot have repeated elements i am pretty sure i have heard the same on GRE Quant concept series
Sorry It’s my bad. You are correct, I cross checked it and a set by definition can’t have repeated elements. One with repeated elements is called a multiset. Yes, a set is a collection of elements where repetition and order are ignored.