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Quick and Easy Math
10. If we look upon the multiplication by 10 and the division by 10 in the manner I have just presented, we see that we are not so much adding and subtracting zeros as merely moving the decimal point. Every time you multiply a number by 10, the decimal point moves one place to the right. H you divide by 10, it moves one place to the left. H you try to multiply by 100, you will find that the decimal point moves two places to the right, while multiplying by 1000 will move it three places to the right. Dividing by 100 will move the decimal point two places to the left, and dividing it by lOOQ will move it three places to the left. Th~ber of places it moves is equal to the number of zeros in the multiplier or diviser; multiplication always involving a rightward movement and division a leftward movement. H you practise this sort of thing. you will see that this explains why the number of zeros at the end of a product is equal to the sum of the zeros at the end of the multiplicand and the multiplier. It also explains why the number of zeros at the end o£l a quotient is equal to the zeros at the end of the dividend minus the zeros at the end of the divisor. But now a question arises. Imagine taking the num¡ her 243 and dividing it by 10. H we write the number with the reserve supply of zeros as 243.000000 (or as many zeros as we want), we might suppose that we ought to move the decimal point leftward again, even though there are no more zeros to the left ot the decimal