Multiplying by 10, 100, 1000 and Their Multiples
To multiply a number by a multiple of 10, multiply the number and the first digit of the multiple of 10; write a zero after the product.
To multiply a number by a multiple of 100, multiply the number and the first digit of the multiple of 100; write 2 zeros after the product.
To multiply a number by a multiple of 1000, multiply the number and the first digit of the multiple of 1000; write 3 zeros after the product.
