Drop the zero or the zeroes from the end of the multiple of 10. For this example, let the multiple of 10 be 60, which becomes 6 after it loses its zero.
Multiply the last number -- the "ones column" number -- of the two-digit number by 6. In this example, let the two-digit number be 57. Multiplying 7 by 6 yields 42.
Multiply the first number -- the "tens column" number -- of the two-digit number by 6, and add a zero to the end of the product. In this example, multiplying 5 by 6 results in 30, which becomes 300 with an added zero.
Add the products. Adding 300 and 42 yields 342.
Add the zero or zeroes that were dropped earlier. By "add" what is meant is inserting the zero or zeroes on the right side of the number 342. Adding a zero to the end of 342 results in 3,420.