Page 61 - Start Up Mathematics_7

9. Multiplication of two decimal numbers: Multiply the two decimal numbers like whole
numbers ignoring the decimal point. Put a decimal point in the product such that the total
number of decimal places is equal to the sum of the decimal places of the two numbers.

10. To divide a decimal number by 10, 100 or 1,000, ...., the digits remain the same, but the
decimal point shifts respectively one, two, three and so on places to the left.

11. Division of a decimal number by another decimal number: Multiply the divisor by 1
followed by as many zeros as there are number of digits in the decimal part of it. Also multiply
the dividend by the same power of 10. Divide the new dividend so obtained by the new divisor
which is a whole number (use long division if necessary).
Review Exercises

Multiple ChoiCe Questions

1. The value of 0.03784 × 1,000 is:
(a) 3.784 (b) 37.84 (c) 378.4 (d) 3,784
2. The place value of the underlined digit in 78.0123 is:
1 1 3 3
(a) (b) (c) (d)
10,000 1,000 1,000 10,000
3. The decimal number 0.72 when represented as a fraction in its lowest term is:

72 36 100 18
(a) (b) (c) (d)
100 50 72 25
4. On subtracting 4.81 from 43.17, we get:
(a) 38.36 (b) 38.81 (c) 38.17 (d) 47.98
5. The number seventeen and seven thousandths in decimal form is:
(a) 17.7000 (b) 17.07 (c) 17.007 (d) 1,77,000.00
6. If on multiplying a decimal number by some power of 10, the place value of a digit changes
from tenths to tens, then the power of 10 is:
(a) 0 (b) 1 (c) 2 (d) 3
7. Amongst the following, the value of expression different from others is:
(a) 6 ÷ 0.21 (b) 60 ÷ 2.1 (c) 0.6 ÷ 0.21 (d) 600 ÷ 21

solve Mentally
True or False

1. A decimal number cannot be divided by another decimal number having the whole part zero.
2. Unlike decimal numbers can be converted into like decimals by adding zeros at the end of
the decimal part.
3. On multiplying a decimal number by a power of 10, it seems that the digits move to the left
of the decimal point by the same number of places as the number of zeros.
4. If there are m and n digits to the right of a decimal point in two numbers then in their product
there are (m + n) or less non-zero digits to the right of the decimal point.
5. Subtracting 0.54 from a number is the same as subtracting 0.054 from it.

6. The product of a decimal number and a whole number can never be a whole number.

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