A cook had 300 carrots in a bucket he was using to cook meals for a restaurant. Before lunch, he had used 2/5 of the carrots. By the end of the day, he had chopped and used 3/5 of the remaining carrots. How many carrots were not used that day?
Use reasoning to answer the following question.
72
Before lunch, the cook had used 2 / 5 * 300 = 120 carrots.

The number of remaining carrots after the cook used 2 / 5 of them is 300 - 120 = 180.

The cook had used 3 / 5 * 180 = 108 of the remaining carrots by the end of the day.

The number of carrots that the cook did not use that day is 180 - 108 = 72.

.

Therefore, the answer is 72