Multiply 78,439 by 5.
A B C D E F
7 8 4 3 9
Given number First Method. The first digit of the product (the A digit) will be equal to one-half of 7 (ignoring the ½ ).
A
3
First digit of product Since the B digit of the given number is odd, the B digit of the product will be 5 plus one-half the C digit of the given number (5 + 4 = 9). The C digit of the given number is even, so that the C digit of the product will be 0 plus one-half the D digit (0 + 2 = 2). The D digit of the product is 0 + 1 = 1. The E digit of the product is 5 + 4 = 9. The F digit of the product Is the units digit in this case, and since the units digit of the given number is odd, the units digit of the product will be 5. The final product is
A B C D E F
3 9 2, 1 9 5 Answer
Second Method. Move the decimal point of the given number one place to the right.
7 8,4 3 9 . 0 becomes 784, 390.
Divide the new number by 2.
784, 390 ÷ 2 = 392, 195 Answer
The same result was obtained with the first method.
