हिंदी

Find the rational number whose decimal expansion is 0.423¯.

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प्रश्न

Find the rational number whose decimal expansion is `0.4bar23`.

योग
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उत्तर

`S_∞ = a/(1-r)`

S = `0.4bar23 => S = 0.4 + 0.023 + 0.00023 + ...  ∞`

`S = 0.4 + 23/10^3 + 23/10^5 + ...  ∞`

`S = 0.4 + 23/10^3 {1 + 10^-2 + 10^-4 + ...  ∞}`

`S = 0.4 + 23/10^3 {1/(1-1/100)}`

`S = 0.4 + 23/10^3 {100/100-1}`

`S = 0.4 + 23/10^3 xx 100/99`

`S = 4/10 + 23/990`

`S = 419/990`

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