How to find multiply two digit number having same ten digit and once digit sum is 10

For solve this problem some condition is required that is

1. First left one digit should same 
2. And one right digit should sum is 10 of two digit

Ex. 21×29,35×35,43×47,42×48,98×92,84×86

Some steps are satisfy for this math short trick

Step 1 :- Multiply the first digit by the first                    digit plus one 

Step 2 :- Multiply the rightmost digit ( if the                  result is single digit put a 0 infront                  of it )

Step 3 :- place the result from step 2 next to                  the result from step 1

Ex. 54 × 56 = 3024

Step 1 :- 5×(5+1) = 5×6 

                              = 30

Step 2 :- 4 × 6 = 24

Step 3 :- 30_24 

            = 3024

Ex. 69 × 61 = 4201

Step 1 :- 6 × (6+1) = 42

Step 2 :- 9 × 1 = 09

               (When the result is single digit then                  put 0 infront of it)

Step 3 :- 42_01 = 4201

   Try some problems. And use this trick but remember condition