To find out how many times Mario's heart beats in a minute, we can use the information that his heart beats 28 times in \( \frac{1}{4} \) of a minute.
To determine the number of beats in a full minute, we can multiply the number of beats in \( \frac{1}{4} \) minute by 4:
\[ \text{Heart beats in 1 minute} = 28 \text{ beats} \times 4 = 112 \text{ beats} \]
Therefore, Mario's heart beats 112 times in a minute.