Answer: 3/8
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Step-by-step explanation:
Let's say this is a 1 by 1 square. The area is 1*1 = 1 square unit. Whatever the area of the triangle is, we divide it over 1 and it will yield the same value as the area of the triangle. In other words, the area of the triangle will be the answer.
Along the top we have 3 ticks to indicate the top segment has been cut into 3+1 = 4 equal parts. The horizontal distance from the the vertical side of the triangle to the peak of the triangle is 3/4 units. This is because we travel 3 ticks out of 4 total. So this is the height when we consider the vertical segment of the triangle to be the base.
The base is 1 unit as it spans the original square's side length
base = 1
height = 3/4
area of triangle = (1/2)*(base*height)
area of triangle = (1/2)*(1*3/4)
area of triangle = 3/8
ratio of triangle area to square area = (triangle area)/(square area)
ratio of triangle area to square area = (3/8)/1
ratio of triangle area to square area = 3/8