The DAV Maths Book Class 5 Solutions and DAV Class 5 Maths Chapter 7 Worksheet 1 Solutions of Multiplication and Division of Decimal Numbers offer comprehensive answers to textbook questions.
DAV Class 5 Maths Ch 7 Worksheet 1 Solutions
Question 1.
Find the product.
(a) 0.3 × 3
Solution:
0.3 × 3
3 × 3 = 9 (Multiply ignoring decimal)
0.3 × 3 = 0.9 (Put decimal point 1 place to the left)
(b) 0.3 × 4
Solution:
0.3 × 4
3 × 4 = 12(Multiply ignoring decimal point)
0.3 × 4 = 1.2 (Put decimal point 1 place to the left)
(c) 0.412 × 2
Solution:
0.412 × 2
412 × 2 = 824 (Multiply ignoring decimal point)
0.412 × 2 = 0.824 (Put decimal point 3 places to the left)
(d) 0.005 × 15
Solution:
0.005 × 15
5 × 15 = 75 (Multiply ignoring decimal point)
0.005 × 75 = .075 (Put decimal point 3 places to the left)
(e) 2.4 × 23
Solution:
2.4 × 23
24 × 23 = 552 (Multiply ignoring decimal point)
2.4 × 23 = 55.2 (Put decimal point 1 place to the left)
(f) 16.3 × 17
Solution:
16.3 × 17
So 163 × 17 = 2771 (Multiply ignoring decimal point)
Now 16.3 × 17 = 277.1 (Put decimal point 1 place to the left)
(g) 71.8 × 248
Solution:
71.8 × 248
718 × 248 = 178064 (Multiply ignoring decimal point)
71.8 × 248 = 17806.4 (Put decimal point 1 place to the left)
(h) 7.37 × 56
Solution:
7.37 × 56
737 × 56 = 41272 (Multiply ignoring decimal point)
7.37 × 56 = 42.72 (Put decimal point 2 places to the left)
(i) 1.001 × 96
Solution:
1.001 × 96
1001 × 19 = 96096 (Multiply ignoring decimal point)
1.001 × 96 = 96.096 (Put decimal point 3 places to the left)
Question 2.
If 3,485 × 16 = 55,760, find
(a) 348.5 × 16
Solution:
348.5 × 16 = 5576.0 or 5576
(b) 34.85 × 16
Solution:
34.85 × 16 = 557.60
(c) 3.485 × 16
Solution:
3.485 × 16 = 55.760
(d) 0.3485 × 16
Solution:
0.3485 × 16 = 5.5760
DAV Class 5 Maths Chapter 7 Worksheet 1 Notes
Whole numbers: Natural numbers along with zero are called whole numbers.
Example: 0, 1, 2, 3, 4, 5, 6, ……….
Decimal numbers: The fractions in which denominators are 10, 100, 1000 etc. are called decimal numbers.
e.g. \(\frac{3}{100}\) = 0.03
In order to multiply two decimal numbers,
- Multiply the numbers ignoring the decimal points.
- Make the decimal places in the product equal to the sum of decimal places in the multiplicand and multiplier.
When we multiply a decimal number by 10,100 or 1000, we just shift the decimal point in the product to the right by as many places as there are zeros in the multiplier.
e.g., 12.342 × 100 = 1234.2
When we divide a decimal number by 10, 100, or 1000 we just shift the decimal point in the quotient to the left by as many places as there are zeros in the divisor.
e.g., 34.46 ÷ 1000 = 0.03446
The product remains the same if the order of two decimal number are changed.
e.g., (a) 4.2 × 2.4 = 10.08
(b) 2.4 × 4.2 = 10.08
The product and division of a decimal number by one is the decimal number itself.
e.g., (a) 4.1 × 1 = 4.1
(b) 3.2 ÷ 1 = 3.2
Product and division of decimal numbers by zero is always zero.
e.g., (a) 3.3 × 0 = 0
(b) 0 ÷ 3.4 = 0
Multiplication of Decimal Numbers
Example 1.
Multiply 0.4 × 3
Solution:
4 × 3 = 12
(Multiply the no. ignoring decimal)
so 0.4 × 3 = 1.2
(The number of decimal places in 0.4 is one. So we keep only one decimal place in the product)
Example 2.
Multiply 3.16 by 0.7
Solution:
316 × 0.7 = 2212
(Multiply ignoring the decimal point)
3.16 × 0.7 = 2.212
(Same number of decimal places in the product as in multiplicand and multiplier)