Answer:
A rational number is defined as a number that can be written as a fraction and a number that terminates.
An irrational number is defined as a number that can't be written as a fraction and a number that has no end.
Explanation:
4/7 is irrational because, in decimal form, it is 0.57142857...
Square root of 30 is also irrational because the square root is 5.47722557...
21 divided by square root of 4 is rational because square root of 4 is 2 and 21 divided 2 is 10.5.
pi is irrational because, in decimal form, it is 3.14159265....
-27 is also rational because it terminates