A. 10 : 6
B. 9 : 21
C. 3 : 9
D. 6 : 10
🧠 Explanation:
A ratio equivalent to 3:7 is 9:21, as 3 × 3 = 9 and 7 × 3 = 21. Knowing this helps students learn ratio concepts, useful in math, science, or real-world tasks like mixing ingredients or financial planning.
