1. **Problem Statement:** We need to find the fraction of the whole large square that is shaded in part (a). 2. **Understanding the figure:** The large square is divided into 4 equal smaller squares, so each smaller square is $\frac{1}{4}$ of the whole. 3. **Focus on the top-left smaller square:** It is divided by its diagonal from top-left to bottom-right, shading the upper left half which forms a right-angled triangle. The area of this triangle is half of the smaller square, so its area is $\frac{1}{2} \times \frac{1}{4} = \frac{1}{8}$ of the whole square. 4. **Inside this triangle, a smaller diamond shape is shaded:** The diamond is inside the triangle, but the problem states it is shaded, so we add its area to the shaded region. 5. **Calculating the diamond's area:** The diamond is formed inside the triangle, and since the problem does not provide exact dimensions, we assume the diamond occupies half the area of the triangle (a common assumption in such problems). 6. **Area of the diamond:** $\frac{1}{2} \times \frac{1}{8} = \frac{1}{16}$ of the whole square. 7. **Total shaded area in (a):** The triangle area plus the diamond area inside it equals $\frac{1}{8} + \frac{1}{16} = \frac{2}{16} + \frac{1}{16} = \frac{3}{16}$. 8. **Final answer:** The fraction of the whole square shaded in part (a) is $\boxed{\frac{3}{16}}$.