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QJEEM24Ma193b: JEE Main 2024 Mathematics - Class 11 JEEM24Ma193b Solution: If , where denotes the greatest integer less than or equal to…

If S={a∈R:∣2a−1∣=3[a]+2{a}}S=\{a \in \mathbf{R}:|2 a-1|=3[a]+2\{a \}\} , where [t][t] denotes the greatest integer less than or equal to tt and {t}\{t\} represents the fractional part of tt , then 72∑a∈Sa is equal to _________.

Step-by-Step Verified Solution

amp;S:{a∈R:∣2a−1∣=3[a]+2{a}}amp;∣2a−1∣=3[a]+2(a−[a])amp;∣2a−1∣=[a]+2a\begin{aligned}& S:\{a \in R:|2 a-1|=3[a]+2\{a\}\} \\& |2 a-1|=3[a]+2(a-[a]) \\& |2 a-1|=[a]+2 a\end{aligned}

Case I: If 0 < a < \frac{1}{2}

amp;1−2a=0+2aamp;⇒a=14\begin{aligned}& 1-2 a=0+2 a \\& \Rightarrow a=\frac{1}{4}\end{aligned}

Case II: If \frac{1}{2} < a < 1

2a−1=0+2a2 a-1=0+2 a

No solution

Case III: If 1 \leq a<2

2a−1=1+2a2 a-1=1+2 a

⇒\Rightarrow No solution

∴\therefore only solution is a=14a=\frac{1}{4}

72∑a∈Sa=72×14=18

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