https://www.gregmat.com/quizzes/quiz/prepswift-distance-rate-x-time (Question 4)
why is 33.02 multipled with 30 instead of 60 to calculate distance travelled in an hour ?
13 \text{ inches} \cdot \frac{2.54 \text{ cm}}{1 \text{ inch}} \cdot \frac{1 \text{ m}}{100 \text{ cm}} \cdot \frac{1 \text{ km}}{1000 \text{ m}} = \frac{13(2.54)}{100 000} \text{ km}
This means the snail travels \frac{13(2.54)}{100 000} \text{ km} per \color{red}{2 \text{ minutes}}. Setting this up as a rate and using dimensional analysis to convert the time to hours yields:
\frac{\frac{13 (2.54)}{100000}}{\color{red}{\cancel{2}} \text{ mins}} \cdot \frac{\color{blue}{\cancelto{30}{60}} \text{ mins}}{1 \text{ hour}} = \frac{33.02 ({\color{purple}{30}})}{100000}
You are multiplying by 30 instead of 60 because the original distance was traveled in \color{red}{2} minutes. When you convert to an hour, \frac{\color{blue}{60}}{\color{red}{2}} simplifies to \color{purple}{30}.