You can make this easier by separating the numbers.
Let's split up 49 first.
You would split this into 40 and 9.
Then, split 45 into 40 and 5.
Multiply the numbers from the ones place (5 and 9) to get 45.
Then multiply the numbers in the tens place (40 and 40).
If you do 4 times 4 it equals 16, and with the two 40's all you have to do is add two zeros., which makes it 1,600.
Then, add both of those numbers (1,600 and 45) up to get 1,645.