To determine which of the numbers is/are irrational, we need to understand what irrational numbers are.
Irrational numbers cannot be written in fractional form but can be written in decimal form.
The square root of a perfect square is a rational number. This means the square root of a non-perfect sqiuare is an irrational number.
So we check the numbers given and determine the ones that are not perfect squares.
Perfect square is a number you can find the square root without getting a decimal
√ 49 = 7 (this is a perfect square)
√54 = √[(2)(3)(9)] = 3√6 (this is not a perfect square)
√64 = 8 (this is a perfect square)
√18 = √(2)(9)
