HCF from Prime Factors | Class 7 Maths Ch 11 | NCERT Ganita Prakash

In this lesson: • 72 pencils and 60 erasers: most identical gift kits? • Breaking both numbers into prime chips • Two circles: shared chips go in the middle • Middle chips 2 × 2 × 3 = 12 kits of 6 pencils and 5 erasers • Why the middle is the highest common factor • HCF of 18 and 24 is 6 • Trap: 36 and 48 share two twos, so the HCF is 12, not 6 • Memory line: HCF lives in the middle NCERT Ganita Prakash, Class 7 — Chapter 11: Finding Common Ground