The HCF of 1020, 850 and 1156 is:

To find the Highest Common Factor (HCF) of 1020, 850, and 1156, follow these steps:

1. First, find the prime factors of each number.

   • The prime factors of 1020 are: 2, 2, 3, 5, 17
   • The prime factors of 850 are: 2, 5, 5, 17
   • The prime factors of 1156 are: 2, 2, 17, 17

2. Identify the common prime factors of all three numbers.

   • The common prime factors are: 2, 17

3. Multiply these common prime factors together to find the HCF.

   • HCF = 2 * 17 = 34

So, the HCF of 1020, 850, and 1156 is 34.