1. **Problem Statement:** Find the Highest Common Factor (HCF) of 16, 20, and 70 using the long division method. 2. **Formula and Rules:** The HCF of two or more numbers is the largest number that divides all of them without leaving a remainder. 3. **Step 1: Find HCF of 16 and 20 using long division:** - Divide 20 by 16: $$20 \div 16 = 1$$ remainder $$4$$ - Now divide 16 by 4: $$16 \div 4 = 4$$ remainder $$0$$ - Since remainder is 0, HCF(16, 20) = 4. 4. **Step 2: Find HCF of the result (4) and the third number (70):** - Divide 70 by 4: $$70 \div 4 = 17$$ remainder $$2$$ - Divide 4 by 2: $$4 \div 2 = 2$$ remainder $$0$$ - Since remainder is 0, HCF(4, 70) = 2. 5. **Final Answer:** The HCF of 16, 20, and 70 is $$2$$.