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It follows from the closure of integers under addition and multiplication.
Any rational number can be expressed as a ratio of two integers, where the second is not zero. So two rational numbers may be expressed as p/q and r/s.
A common multiple of their denominators is qs. So the numbers could also have been expressed as ps/qs and qr/qs.
Both these have the same denominator so their sum is (ps + qr)/qs.
Now, because the set of integers is closed under multiplication, ps, qr and qs are integers and because the set of integers is closed under addition, ps + qr is an integer.
Thus the sum has been expressed as a ratio of two integers, ps + qr, and qs and so it is a rational number.
What else can I help you with?
Is the product of two rational numbers irrational?
The product of two rational numbers is always a rational number.
Is multiplication of a whole number associative?
Yes. Multiplication of integers, of rational numbers, of real numbers, and even of complex numbers, is both commutative and associative.
What s happens when rational numbers are multplied?
The product of two rational numbers is always a rational number.
Why does a rational number plus a rational number or a rational number multiplied by a rational number equal to rational number?
The way in which the binary functions, addition and multiplication, are defined on the set of rational numbers ensures that the set is closed under these two operations.
How are multiplying and dividing rational numbers related?
Dividing by a rational number (other than zero) is simply multiplication by its reciprocal.
Is a rational number closed for addition and for multiplication?
A rational number is not. But the set of ALL rational numbers is.
Are rational numbers closed under multiplication?
Rational numbers are closed under multiplication, because if you multiply any rational number you will get a pattern. Rational numbers also have a pattern or terminatge, which is good to keep in mind.
Can you add two rational numbers and get an irrational number?
No. The set of rational numbers is closed under addition (and multiplication).
What is the combination of rational numbers and irrational?
It the combination is multiplication and the rational number is 0, then the result is rational. Otherwise it is irrational.
Is the product of two rational numbers irrational?
The product of two rational numbers is always a rational number.
Is multiplication of a whole number associative?
Yes. Multiplication of integers, of rational numbers, of real numbers, and even of complex numbers, is both commutative and associative.
What s happens when rational numbers are multplied?
The product of two rational numbers is always a rational number.
Does there exist an irrational number such that its square root is rational?
No, and I can prove it: -- The product of two rational numbers is always a rational number. -- If the two numbers happen to be the same number, then it's the square root of their product. -- Remember ... the product of two rational numbers is always a rational number. -- So the square of a rational number is always a rational number. -- So the square root of an irrational number can't be a rational number (because its square would be rational etc.).
Can half of an irrational number be rational?
No, it cannot. The product of a rational and irrational is always irrational. And half a number is equivalent to multiplication by 0.5
Why does a rational number plus a rational number or a rational number multiplied by a rational number equal to rational number?
The way in which the binary functions, addition and multiplication, are defined on the set of rational numbers ensures that the set is closed under these two operations.
How are multiplying and dividing rational numbers related?
Dividing by a rational number (other than zero) is simply multiplication by its reciprocal.
Is a fraction never a rational number?
Fractions where both the numerator and divisor are rational numbers are always rational numbers.
