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.
Problem 1 :
The side of a square is 3.2 cm. Find its perimeter.
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?
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
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.
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.
Apart from the stuff given above, 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 :
We always appreciate your feedback.
You can also visit the following web pages on different stuff in math.
Negative exponents rules
APTITUDE TESTS ONLINE
ACT MATH ONLINE TEST
TRANSFORMATIONS OF FUNCTIONS
ORDER OF OPERATIONS
MATH FOR KIDS
Word problems on linear equations
Trigonometry word problems
Word problems on mixed fractrions
Ratio and proportion shortcuts
Converting repeating decimals in to fractions