There are two main methods to multiply/divide decimals without a calculator.
I. Calculating using fractions.
One way is to convert the decimal into a fraction, and then multiply/divide fractions. As you know, when you are multiplying fractions, just multiply the denominator by denominator, and the numerator by numerator. Then, if possible, you can simplify the fraction, and then convert the fraction back to the decimal by dividing numerator by denominator.
If you are dividing fractions, switch the numerator and denominator of the divisor. Then, you can take the same steps as multiplication afterwards.
II. Calculate it as if you are multiplying/dividing whole numbers.
Another way is to ignore the decimal points, and first multiply/divide as if you are calculating with whole numbers. If you are multiplying two decimals, count the number of digits after the decimal in each factor. Then, you can add up the number of digits after the decimal, and put the same number of digits behind the decimal in the product.
Likewise, if you are dividing two decimals, count the number of digits after the decimal in each factor. Then, subtract the divisor's number of digits after the decimal by the dividend's. Afterwards, put the same number of digits behind the decimal in the product.
I have added an image to clarify my answer to your question.
I personally recommend the second method as it is usually faster, but you can use whichever method that suits you.
Hi Rose, thank you for your question.
There are two main methods to multiply/divide decimals without a calculator.
I. Calculating using fractions.
One way is to convert the decimal into a fraction, and then multiply/divide fractions. As you know, when you are multiplying fractions, just multiply the denominator by denominator, and the numerator by numerator. Then, if possible, you can simplify the fraction, and then convert the fraction back to the decimal by dividing numerator by denominator.
If you are dividing fractions, switch the numerator and denominator of the divisor. Then, you can take the same steps as multiplication afterwards.
II. Calculate it as if you are multiplying/dividing whole numbers.
Another way is to ignore the decimal points, and first multiply/divide as if you are calculating with whole numbers. If you are multiplying two decimals, count the number of digits after the decimal in each factor. Then, you can add up the number of digits after the decimal, and put the same number of digits behind the decimal in the product.
Likewise, if you are dividing two decimals, count the number of digits after the decimal in each factor. Then, subtract the divisor's number of digits after the decimal by the dividend's. Afterwards, put the same number of digits behind the decimal in the product.
I have added an image to clarify my answer to your question.
I personally recommend the second method as it is usually faster, but you can use whichever method that suits you.
Does this answer your question?