Page 94 - Math Skill - 5

92 Maths

The value of each digit has increased by one place.
Kavita spent ` 87.50 on the notebooks.

For example,

1. 4.62 × 10 = 46.2 Value of each digit has increased by one place.

2. 5.869 × 100 = 586.9 Value of each digit has increased by 2 places.

3. 7.203 × 1000 = 7203 Decimal point may not be given as it has become a whole number.

4. 16.80 × 100 = 1680 A zero is put to make 2 places of decimals.

Multiplication of Two Decimals

To multiply two decimals, we follow these steps:

Step 1: Multiply the two decimals without the decimal point, just like ordinary numbers.
Step 2: In the product, place the decimal point so that the number of decimal places in the
product is equal to the sum of the decimal places in the given decimals.

Let’s learn through examples.

Let’s Attempt

Example 1: Multiply 35.7 by 0.34.

Solution: First, we multiply 357 by 34.

3 5 7
× 3 4
1 4 2 8 Sum of the decimal places = 1 + 2 = 3
+ 1 0 7 1 0 Thus, 35.7 × 0.34 = 12.138

1 2 1 3 8
Example 2: Multiply 0.055 × 6.34 × 8.2.

Solution: 6 3 4 3 4 8 7 0
× 5 5 × 8 2
3 1 7 0 6 9 7 4 0
+ 3 1 7 0 0 + 2 7 8 9 6 0 0
3 4 8 7 0 2 8 5 9 3 4 0

Sum of all the decimal places in three numbers = 3 + 2 + 1 = 6
Thus, 0.055 × 6.34 × 8.2 = 2.859340.

Exercise 6.6

1. Find the products.
(a) 23.5 × 7 (b) 0.941 × 25 (c) 105.75 × 373

(d) 83.85 × 85 (e) 91.85 × 182 (f) 0.375 × 292