Final answer:
The dimensions of the rectangular poster are 14 inches by 21 inches.
Step-by-step explanation:
To find the dimensions of the poster, let's assume the width of the poster is 'x' inches. According to the problem, the length of the poster is 1.5 times longer than the width. So the length of the poster would be 1.5x inches.
Now, we know that the area of a rectangle is found by multiplying its length and width. So we can set up the equation: x * (1.5x) = 294.
Simplifying the equation, we have 1.5x^2 = 294. Dividing both sides by 1.5, we get x^2 = 196. Taking the square root of both sides, we find x = 14 inches.
Therefore, the dimensions of the poster are 14 inches by 1.5 times longer, which is 21 inches.