The plane flies 5 km in 1/3 minute. How many kilometers does an airplane fly in half an hour?

If one hour has 60 minutes, then half an hour has 30 minutes.
Let’s make the proportion:
1/3 minutes – 5 km.;
30 minutes. – x km.
From the main property of proportion: the product of the extreme terms of the proportion is equal to the product of the middle terms, it follows:
1/3 * x = 5 * 30;
1/3 * x = 150;
x = 150: 1/3;
x = 150 * 3;
x = 450
Answer: 450 km.