1. **State the problem:** Multiply 1.78 by 4. 2. **Formula used:** Multiplication of two numbers is given by $$a \times b$$. 3. **Apply the formula:** Here, $$a = 1.78$$ and $$b = 4$$. 4. **Calculate:** $$1.78 \times 4 = 7.12$$ 5. **Explanation:** Multiplying 1.78 by 4 means adding 1.78 four times or scaling 1.78 by a factor of 4. 6. **Final answer:** $$\boxed{7.12}$$