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IPMAT Rohtak 2020 PYQsQuantitative Ability. Free, no login required.

Solution

✅ Correct Option: 3

383=5487238^3 = 54872 and 393=5931939^3 = 59319

5555555555 lies between them, so 555553\sqrt[3]{55555} is between 3838 and 3939.


Quick estimate: N3≈a+N−a33a2\sqrt[3]{N} \approx a + \dfrac{N - a^3}{3a^2}, with a=38a = 38:

555553≈38+55555−548723×382\sqrt[3]{55555} \approx 38 + \dfrac{55555 - 54872}{3 \times 38^2}

=38+6834332= 38 + \dfrac{683}{4332}

≈38+0.1577\approx 38 + 0.1577

=38.1577= 38.1577


This estimate is very slightly above the true value (by less than 0.0010.001), so:

555553=38.157…\sqrt[3]{55555} = 38.157\ldots

Rounded to two decimal places, 555553=38.16\sqrt[3]{55555} = 38.16.

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