-->

Polynomials

Question
CBSEENMA9001467

 You know that 1 over 7 equals 0. top enclose 142857
 Can you predict what the decimal expansions of 

2 over 7 comma space 3 over 7 comma space 4 over 7 comma space 5 over 7 comma space 6 over 7
 are, without actually doing the long division? If so, how?



[Hint: Study the remainders while finding the value of 1 over 7 carefully.]

Solution

Yes! We can predict the decimal expansions of 2 over 7 comma space 3 over 7 comma space 4 over 7 comma space 5 over 7 comma space 6 over 7 without actually doing the long division as follows:
                                 downwards arrow
7 space right parenthesis space 1.0000000 space left parenthesis space 0.1428571.....
space space space space bottom enclose space 7 space space end enclose
space space space space space 30 space
space space space space bottom enclose space 28 space space end enclose
space space space space space space space 20 space space leftwards arrow
space space space space space space bottom enclose space 14 space space end enclose
space space space space space space space space 60
space space space space space space space bottom enclose space 56 space space end enclose
space space space space space space space space space 40
space space space space space space space space bottom enclose space 35 space space end enclose
space space space space space space space space space space 50
space space space space space space space space space bottom enclose space 49 space space end enclose space
space space space space space space space space space space space 10 space
space space space space space space space space space space bottom enclose space space 7 space space end enclose
space space space space space space space space space space space space 3 space
To predict the decimal expansion of 2 over 7 locate when the remainder becomes 2 and respective quotient (here it is 2). Then write the new quotient beginning from there using the repeating digits 1, 4, 2, 8, 5, 7.
therefore space space space space space 2 over 7 space equals space 0. top enclose 285714


Similarly,
           space space space space space space space space space space 3 over 7 equals space 0. top enclose 428571
space space space space space space space space space space 4 over 7 equals space 0. top enclose 571428
space space space space space space space space space space 5 over 7 equals space 0. top enclose 714285
a n d space space space space space 6 over 7 equals space 0. top enclose 857142
 

Some More Questions From Polynomials Chapter

Find two rational numbers between 0.1 and 0.2.