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Let a be a positive real number such that ∫ _0^a e^x-[x]dx=10e-9 where, [x] is the greatest integer less than or equal to x. Then, a is equal to:

JEE Main 2021 — Mathematics Calculus

2021mcqhard

Let aaa be a positive real number such that ∫0aex−[x]dx=10e−9\displaystyle {\int }_{0}^{a}{e}^{x-[x]}dx=10e-9∫0a​ex−[x]dx=10e−9 where, [x][x][x] is the greatest integer less than or equal to xxx. Then, aaa is equal to:

Official previous-year question

Held on 20 Jul 2021 · Verified 6 Jul 2026.

Options

  1. A

    10−loge(1+e)10-{\mathrm{log}}_{e}(1+e)10−loge​(1+e)

  2. B

    10+loge210+{\mathrm{log}}_{e}210+loge​2

  3. C

    10+loge310+{\mathrm{log}}_{e}310+loge​3

  4. D

    10+loge(1+e)10+{\mathrm{log}}_{e}(1+e)10+loge​(1+e)

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