Ratios: From Basics to Challenges

BASIC LEVEL: In a class of 25 students, 15 are girls and 10 are boys. What is the ratio of girls to boys? INTERMEDIATE LEVEL: A recipe calls for 3 cups of flour to 2 cups of sugar. If you want to make a larger batch using 9 cups of flour, how much sugar do you need? ADVANCED CHALLENGE: Two gears are connected. The first gear has 24 teeth and rotates 5 times per minute. The second gear has 40 teeth. How many times does the second gear rotate per minute? RATIO REMINDER: A ratio compares two quantities by division. It can be written as a:b, a/b, or 'a to b'.