43 × 15 = 645.
First, set up the long multiplication.
Second, calculate 3 × 5, which is 15. Since 15 is two-digit, carry the first digit 1 to the next column.
Third, calculate 4 × 5 which is 20. Since 21 is two-digit, carry the first digit 2 to the next column.
Fourth, bring down the carry digit of 2.
Fifth, calculate 3 × 1, which is 3.
Sixth, calculate 4 × 1, which is 4.
Seventh, calculate 215 + 430, which is 645.
Eighth, therefore, 43 × 15 = 645.
Or.. an easier way is to use a calculator. They always come in handy when doing multiplication.