Estimate that 500 x 4 = 2,000
+ 50 x 4 = 200
+ 6 x 4= 24
so you can estimate somewhere between 2,000-2,224
To multiply:
Start with 6 x 4 which equals 24.
You can only put the last letter in the answer and carry the two over the second 5.
Next comes 5 x 4 + the 2 you carried, so 22.
Write down a two in the answer and carry the next two.
5 x 4 + 2 again is 22, this time, since there are no numbers left to carry the 2 over to, you're left with 2,224.