1.

Find the rational number whose decimal expansion is 0.42\(\bar 3\)

Answer»

Let, x = 0.4233333333….. ….equation 1 

As 3 is the repeating term, so in all such problems multiply both sides of the equation with a number such that complete repetitive part of number comes after the decimal.

∴ multiplying equation 1 with 100 in both sides, we have – 

100x = 42.3333333333… …equation 2 

Subtracting equation 1 from equation 2,we get

100x – x = 42.3333333… - 0.423333333… 

⇒ 99x = 41.91 {as letter terms gives zero only 42.33-0.42 gives result} 

∴ x = 41.91/99 

⇒ x = 4191/9900

Note: We can also solve these problems using geometric progression, but the above method is much simpler.



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