# MULTIPLICATION OF DECIMALS

## Multiplication of decimals - Introduction

Multiplication of decimals :

Lily purchased 2.5 lbs fruits at the rate of \$3.50 per lb. How much money should she pay?

Certainly it would be \$(2.5 × 3.50). Both 2.5 and 3.5 are decimal numbers.

Now, we have come across a situation where we need to know how to multiply two decimals. So we now learn the multiplication of two decimal numbers.

Now, let us find 1.5 × 4.3

Multiplying 15 and 43, we get 645.

Both, in 1.5 and 4.3, there is 1 digit to the right of the decimal point. So, count 2 digits from the right and put a decimal point.

So, we get 1.5 x 4.3  =  6.45

While multiplying 1.43 and 2.1, you will first multiply 143 and 21. For placing the decimal in the product obtained, you will count 2 + 1 = 3 digits starting from the right most digit.

Thus 1.43 × 2.1 = 3.003.

## Multiplication of decimals - Practice problems

Problem 1 :

The side of a square is 3.2 cm. Find its perimeter.

Solution :

All the sides of a square are equal.

Length of each side = 3.2 cm.

Perimeter of a square = 4 × side

Thus, perimeter = 4 × 3.2 = 12.8 cm.

Problem 2 :

The length of a rectangle is 6.3 cm and its breadth is 3.2 cm. What is the area of the rectangle?

Solution :

Length of the rectangle = 6.3 cm

Breadth of the rectangle = 3.2 cm.

Area of the rectangle = ( length) × (breath)

= 6.3 × 3.2

= 20.16 cm²

## Multiplying decimals by 10 100 and 1000

Lily observed that

3.7  =  37/10

3.72  =  372/100

3.723  =  23723/1000

Thus, she found that depending on the position of the decimal point the decimal number can be converted to a fraction with denominator 10 , 100 or 1000.

Now let us see what would happen if a decimal number is multiplied by 10 or 100 or 1000.

For example,

3.23 x 10  =  (323/100) x 10  =  323/10  =  32.3

Decimal point shifted to the right by one place since 10 has one zero.

3.23 x 100  =  (323/100) x 100  =  32.3

Decimal point shifted to the right by one place since 100 has two zeros.

3.23 x 1000  =  (323/100) x 1000  =  323 x 10  =  3230

Decimal point shifted to the right by one place since 1000 has three zeros. After having gone through the stuff given above, we hope that the students would have understood "Multiplying decimals".

Apart from the stuff given in this section, if you need any other stuff in math, please use our google custom search here.

If you have any feedback about our math content, please mail us :

v4formath@gmail.com

You can also visit the following web pages on different stuff in math.

WORD PROBLEMS

Word problems on simple equations

Word problems on linear equations

Algebra word problems

Word problems on trains

Area and perimeter word problems

Word problems on direct variation and inverse variation

Word problems on unit price

Word problems on unit rate

Word problems on comparing rates

Converting customary units word problems

Converting metric units word problems

Word problems on simple interest

Word problems on compound interest

Word problems on types of angles

Complementary and supplementary angles word problems

Double facts word problems

Trigonometry word problems

Percentage word problems

Profit and loss word problems

Markup and markdown word problems

Decimal word problems

Word problems on fractions

Word problems on mixed fractrions

One step equation word problems

Linear inequalities word problems

Ratio and proportion word problems

Time and work word problems

Word problems on sets and venn diagrams

Word problems on ages

Pythagorean theorem word problems

Percent of a number word problems

Word problems on constant speed

Word problems on average speed

Word problems on sum of the angles of a triangle is 180 degree

OTHER TOPICS

Profit and loss shortcuts

Percentage shortcuts

Times table shortcuts

Time, speed and distance shortcuts

Ratio and proportion shortcuts

Domain and range of rational functions

Domain and range of rational functions with holes

Graphing rational functions

Graphing rational functions with holes

Converting repeating decimals in to fractions

Decimal representation of rational numbers

Finding square root using long division

L.C.M method to solve time and work problems

Translating the word problems in to algebraic expressions

Remainder when 2 power 256 is divided by 17

Remainder when 17 power 23 is divided by 16

Sum of all three digit numbers divisible by 6

Sum of all three digit numbers divisible by 7

Sum of all three digit numbers divisible by 8

Sum of all three digit numbers formed using 1, 3, 4

Sum of all three four digit numbers formed with non zero digits

Sum of all three four digit numbers formed using 0, 1, 2, 3

Sum of all three four digit numbers formed using 1, 2, 5, 6

Featured Categories

Math Word Problems

SAT Math Worksheet

P-SAT Preparation

Math Calculators

Quantitative Aptitude

Transformations

Algebraic Identities

Trig. Identities

SOHCAHTOA

Multiplication Tricks

PEMDAS Rule

Types of Angles

Aptitude Test 