NCERT Chapter Notes - 2 Multiplication and Division on Fraction, Maths, Class 7 PDF Download

Multiplication and Division on Fraction

To multiply a fraction by a whole number, multiply the whole number by the numerator of the fraction.

Multiplication of fractions:

To multiply a fraction by a whole number, multiply the whole number by the numerator of the fraction.

Eg: While multiplying a whole number by a mixed fraction, change the mixed fraction into an improper fraction.

Eg: To multiply two fractions, multiply their numerators and denominators.

Eg:

When two proper fractions are multiplied, the product is less than each of the individual fractions. When two improper fractions are multiplied, the product is greater than each of the individual fractions.

Division of fractions:

To obtain the reciprocal of a fraction, interchange the numerator with the denominator.

Eg:  

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To divide a whole number by a fraction, take the reciprocal of the fraction and then multiply it by the whole number.

Eg: To divide a fraction by a whole number, multiply the fraction by the reciprocal of the whole number.

Eg: To divide a fraction by a fraction, multiply the first fraction by the reciprocal of the second fraction.

Multiplication and Division on Decimals

Ignore the decimals and multiply the two numbers.

Multiplication of decimals:

1. To multiply a whole number by a decimal number, follow these steps:
2. Ignore the decimals and multiply the two numbers.
3. Count the numbers of digits to the right of decimal point in the original decimal number.
4. Insert the decimal, from right to left, in the answer by the same count.

Eg: (i) 3×0.2=0.6  (ii) 3×0.4=1.2

1. To multiply a decimal number by a decimal number, follow these steps:
2. Ignore the decimals and multiply the two numbers.
3. Count the number of digits to the right of decimal point in both the decimal numbers.
4. Add the number of digits counted and insert the decimal, from right to left, in the answer by the same count.

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Eg: (i) 0.2×0.7=0.14 (ii) 0.9×0.02=0.018

 To multiply a decimal number by 10, 100 or 1000, follow these steps:-
1. While multiplying a decimal number by 10, retain the original number and shift the decimal to the right by one place.
2. While multiplying a decimal number by 100, retain the original number and shift the decimal to the right by two places.
3. While multiplying a decimal number by 1000, retain the original number and shift the decimal to the right by three places.

Division of decimals:

1. To divide a decimal number by a whole number, follow these steps:
2. Convert the decimal number into a fraction.
3. Take the reciprocal of the divisor.
4. Multiply the reciprocal by the fraction.

Eg:

1. To divide a decimal number by another decimal number, follow these steps:
2. Convert both the decimal numbers into fractions.
3. Take the reciprocal of the divisor.
4. Multiply the reciprocal by the fraction.