How do you decide if the number terminates?

How do you decide if or not a fraction is terminating?

11 Answers

36
rahul ·

if the denominator of a fraction can be written in the form of 2m.5n where m,n belongs to positive integers... then the fraction is terminating or else non-terminating.....

1
jee12 ·

but before checking for 2 and 5 it shud b in lowest form

obviously!!!

36
rahul ·

thanks fr adding the most imp part...

49
Subhomoy Bakshi ·

@Rahul: 31 is also a fraction! [3]

and u said:
"......in the form of 2m.5n where m,n belongs to positive integers......"

Isn't that an integer?

1
jee12 ·

@SUBHOMOY

bhaiya i don't think 3/1 is a fraction

yes its a rational number

the very time in junior classes i heard fraction it was not 3/1!!

we can write it that way but its rational no..

i don't think we need to worry about that 3/1

(BUT I GUESS NISHANT SIR EXPECTED A BETTER ANS)

49
Subhomoy Bakshi ·

oops! i had intended to write 32

62
Lokesh Verma ·

Good work rahul... Neone for a proof?

30
Ashish Kothari ·

Let the fraction in its lowest form be of the form xy, x and y being integers.

Now let y = 2m.5n , m and n are also non-negative integers.

multiplying Numerator and denominator by 2n.5m

then = xy = x.2n.5m 10m+n which clearly terminates.

In any other case, where the denominator has a factor pr, where p is a prime other than 2 and 5 and r is a positive integer, then the denominator cannot be represented in the form 10k, and the fraction will be recurrent,non-terminating decimal.

11
Khilen Khara ·

The proof of this lies in the fact that every terminating decimal
has the form n/10^e, for some e >= 0 (e is the number of places to
the right that the decimal point must be moved to give you an integer,
and n is that integer), and every fraction of that form has a
terminating decimal found by writing down n and moving the decimal
point e places to the left. Now when you cancel common factors from
n/10^e = n/(2*5)^e = n/(2^e*5^e), it may reduce the exponents
in the denominator

62
Lokesh Verma ·

A simple part left to prove..... .

How do you prove your claim that every terminating number has to have only 10^k as the denominator?

21
Shubhodip ·

Let the fraction be ab ,where gcd(a,b) = 1. this will terminate <=> there exists some integer k>0 such that 10kab is an integer. which means b|10k. bcz gcd(a,b) =1. We get Rahuls answer

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