The term "closed" in math means that if you take two items from a set, do some operation, then you'll always get another value in the same set (sometimes you may get the same value as used before). For example, adding two whole numbers leads to another whole number. We therefore say "the set of whole numbers is closed under addition". This applies to integers as well because integers are positive and negative whole numbers. So we can say that integers are closed under addition.
Integers are not closed under division. Take two integers like 2 an 5 and divide: 2/5 = 0.4 which is not an integer. Integers don't have decimal parts.
The set of whole numbers is {0,1,2,3,...} and we can subtract the two values 1 and 2 to get 1-2 = -1. The order matters here. Subtracting a larger value from a smaller leads to a negative. The value -1 is not in the set of whole numbers. So we can say that whole numbers is not closed under subtraction
Finally, the set of irrational numbers is closed under addition. Adding any two irrational numbers leads to another irrational number. For instance, pi+sqrt(2) = 3.142 + 1.414 = 4.556; I'm using rounded decimals as approximate values. An irrational number is one where we cannot write it as a fraction of integers. Contrast that with a rational number in which we can write it as a fraction of integers. Example: 10 = 10/1 is a rational number.
Answer:
24
Step-by-step explanation:
(72/-9) / (-1/3)
72/-9) x (-3/1)
(72)*(-3) = - 216/ -9
= 24
Well take 500 and subtract the 236 then divide the rest by two and the answer should be 132
Answer:
-----×1/72
Step-by-step explanation:
The <em>order of operations</em> says do these operations in order left to right. Please note that ÷ means the same as / unless you define it otherwise in your problem statement.
If you intend the ÷ symbol to be used to indicate everything to its left is divided by everything to its right, it is appropriate to use parentheses for that grouping, as in ...
(-----×1/4)÷(6×3/9) = (-----×1/4)÷2 = -----×1/8
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Here, we're going to evaluate what you have written according to the usual rules as described above.
(-----×1/4)÷6×3/9 = -----×1/24×3/9 = -----×(3/24)/9
= -----×1/8/9
= -----×1/72
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<em>Comment on the arithmetic</em>
Fractions are multiplied and divided in the usual way:
a/b×c = (a×c)/b
a/b/c = (a/b) × (1/c) = a/(b×c)
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<em>Comment on fractions and parentheses</em>
Please note that parentheses are required on any numerator or denominator that consists of anything other than a single number or variable. (The exception is the case where the numerator is a product, because a·b/c = (a·b)/c with or without the parentheses.)
