Decimals and its Operations
Decimal number is an another way to write a fraction. For example, $ 4.25, $ 0.25, the number after the decimal or right side from the decimal is part of one dollar. It can also be written as \[\frac{25}{100}\] of a dollar. The base of decimal number system is 10 and Indo - Arabic number system is base 10 number system. Base 10 or decimal number system can always change the place value of the number by one spot, either multiplying or dividing by 10. It is more clear from the example given below:
Decimal point
The decimal point is the most important part of a decimal number. It is exactly to the right of the units position.
Like and Unlike Decimals
The decimals having the same number of digits to the right of decimal point are called like decimals, otherwise decimals are unlike. For example 10.52, 0.63, 258.69, 35.74 are like-decimals whereas 11.205, 4.23, 7.852, 14.00087 are unlike decimals.
Terminating and Non-Terminating and Repeating Decimals
If the decimal representation of a fraction \[\frac{p}{q}\] comes to an end then the decimal we obtain, is called terminating decimals. Important note: A fraction \[\frac{p}{q}\] is a terminating decimal, if prime factors of q are 2 and 5 only.
\[2\frac{3}{5}=2.6\] is a terminating decimal.
Non - terminating and repeating decimals: A decimal in which digit or a set of digits repeats periodically is called non - terminating and repeating decimals. For example, \[\frac{1}{3}=0.3333333.....=\text{ }0.\overline{3}\]and\[\frac{3}{11}=0.272727.......=0.\overline{27}\] are non-terminating and repeating decimals.
Find the terminating decimals from the following fractions:
\[\frac{23}{25},\frac{219}{175},\frac{337}{80},\frac{29}{198},\frac{19}{512}\]
(a) \[\frac{23}{25},\frac{219}{175},\frac{337}{80}\]
(b) \[\frac{337}{80},\frac{29}{198},\frac{19}{512}\]
(c) \[\frac{219}{175},\frac{337}{80},\frac{29}{198}\]
(d)\[\frac{23}{25},\frac{337}{80},\frac{19}{512}\]
(e) None of these
Answer: (d)
Explanation
The denominators of fractions are 25,175, 80,198, 512 and their prime factors are: \[25=5\times 5\]
\[175=5\times 5\times 7,\]\[80=2\times 2\times 2\times 2\times 5,\]\[198=2\times 3\times 3\times 11\]
\[512\text{ }=2\times 2\times 2\times 2\times 2\times 2\times 2\times 2\times 2\]
Here we observe that the prime factors of 25, 80 and 512 have only 2 and 5.
Hence\[\frac{23}{25},\frac{337}{80},\frac{19}{512}\] are terminating decimal.
Express one second into hour.
(a) .0025 hours
(b) 1.0256 hours
(c) .00027 hours
(d) 1.000126 hours
(e) None of these
Answer: (c)
Explanation
One second \[=\frac{1}{60\times 60}=.00027\] hours
Which one of the following fractions is in ascending order?
(a) \[\frac{16}{19},\frac{11}{14},\frac{17}{22}\]
(b) \[\frac{11}{14},\frac{16}{19},\frac{17}{22}\]
(c) \[\frac{17}{22},\frac{11}{14},\frac{16}{19}\]
(d) \[\frac{16}{19},\frac{17}{22},\frac{11}{14}\]
(e) None of these
Answer: (c)
Explanation
\[\frac{16}{19}=0.842,\frac{17}{22}=0.773\And \frac{11}{14}=0.786.\]
\[\therefore 0.77<0.786<0.842\frac{17}{22}<\frac{11}{14}<\frac{16}{19}\]
The LC.M. of 3, 0.09 and 2.7 is:
(a) 2.7
(b) 1.27
(c) .027
(d) 0.27
(e)
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