IKMC 2027 - Grades 7-8 - Self-study SET 4 - Thematic Batch 3 Question 22

Chip and Dale collect nuts for their nest. Dale proposes that each of them eat 2 nuts a day, and Chip calculates that the stock would last 15 days. Instead, Dale eats 2 nuts a day and Chip only 1. How many extra days will the stock last?