Notes On Multiplication and Division on Decimals - CBSE Class 7 Maths
Multiplication of decimals Steps to multiply a whole number by a decimal number: Step 1: Ignore the decimals and multiply the two numbers. Step 2: Count the number of digits to the right of decimal point in the original decimal number. Step 3: Insert the decimal in the answer by the same count from right to left. e.g. (i)   3 × 0.2 = 0.6  (ii) 3 × 0.4 = 1.2 Steps to multiply a decimal number by a decimal number: Step 1: Ignore the decimals and multiply the two numbers. Step 2: Count the number of digits to the right of decimal point in both the decimal numbers Step 3: Add the number of digits counted and insert the decimal in the answer by the same count from right to left. e.g. (i) 0.2 × 0.7 = 0.14 (ii) 0.9 × 0.02 = 0.018 Multiplication of a decimal number by 10, 100 or 1000: For multiplying a decimal number by 10, retain the original number and shift the decimal to the right by one place For multiplying a decimal number by 100, retain the original number and shift the decimal to the right by two places For multiplying a decimal number by 1000, retain the original number and shift the decimal to the right by three places Division of decimals Steps to divide a decimal number by a whole number: Step 1: Convert the decimal number into a fraction. Step 2: Find the reciprocal of the divisor. Step 3: Multiply the fraction by the reciprocal . e.g. 0.14 ÷ 3 = $\frac{\text{14}}{\text{100}}$ × $\frac{\text{1}}{\text{3}}$ = $\frac{\text{14}}{\text{300}}$   Steps to divide a decimal number by another decimal number: Step 1: Convert both the decimal numbers into fractions. Step 2: Find the reciprocal of the divisor. Step 3: Multiply the fraction by the reciprocal. e.g. 0.45 ÷ 0.15 = $\frac{\text{45}}{\text{100}}$ ÷ $\frac{\text{15}}{\text{100}}$= $\frac{\text{45}}{\text{100}}$× $\frac{\text{100}}{\text{15}}$= 3

#### Summary

Multiplication of decimals Steps to multiply a whole number by a decimal number: Step 1: Ignore the decimals and multiply the two numbers. Step 2: Count the number of digits to the right of decimal point in the original decimal number. Step 3: Insert the decimal in the answer by the same count from right to left. e.g. (i)   3 × 0.2 = 0.6  (ii) 3 × 0.4 = 1.2 Steps to multiply a decimal number by a decimal number: Step 1: Ignore the decimals and multiply the two numbers. Step 2: Count the number of digits to the right of decimal point in both the decimal numbers Step 3: Add the number of digits counted and insert the decimal in the answer by the same count from right to left. e.g. (i) 0.2 × 0.7 = 0.14 (ii) 0.9 × 0.02 = 0.018 Multiplication of a decimal number by 10, 100 or 1000: For multiplying a decimal number by 10, retain the original number and shift the decimal to the right by one place For multiplying a decimal number by 100, retain the original number and shift the decimal to the right by two places For multiplying a decimal number by 1000, retain the original number and shift the decimal to the right by three places Division of decimals Steps to divide a decimal number by a whole number: Step 1: Convert the decimal number into a fraction. Step 2: Find the reciprocal of the divisor. Step 3: Multiply the fraction by the reciprocal . e.g. 0.14 ÷ 3 = $\frac{\text{14}}{\text{100}}$ × $\frac{\text{1}}{\text{3}}$ = $\frac{\text{14}}{\text{300}}$   Steps to divide a decimal number by another decimal number: Step 1: Convert both the decimal numbers into fractions. Step 2: Find the reciprocal of the divisor. Step 3: Multiply the fraction by the reciprocal. e.g. 0.45 ÷ 0.15 = $\frac{\text{45}}{\text{100}}$ ÷ $\frac{\text{15}}{\text{100}}$= $\frac{\text{45}}{\text{100}}$× $\frac{\text{100}}{\text{15}}$= 3

Next