Add the mixed numbers 1 rac516 + 3 rac34.

We have $1\frac{5}{16} + 3\frac{3}{4}$.
Add the whole numbers:

$$1 + 3 = 4$$

Add the fractions:

$$\frac{5}{16} + \frac{3}{4}$$

The denominators are 16 and 4. The least common multiple of 16 and 4 is 16.
Convert $\frac{3}{4}$ to an equivalent fraction with a denominator of 16:

$$\frac{3}{4} = \frac{3 \times 4}{4 \times 4} = \frac{12}{16}$$

$$4 + 1\frac{1}{16} = (4 + 1) + \frac{1}{16} = 5 + \frac{1}{16} = 5\frac{1}{16}$$

The fraction $\frac{1}{16}$ is already in its simplest form.

The final answer is $5\frac{1}{16}$.