If \(\int_0^n[x] \mathrm{dx}=66\), then \(n=\)
If \(\int_0^n[x] \mathrm{dx}=66\), then \(n=\)
- 24
- 9
- 12
- 7
Solution
\(\begin{aligned}
& \int_0^n[x] d x=\int_0^1 0 d x+\int_1^2 1 d x+\int_2^3 2 d x+\ldots \ldots+ \\
& \int_{n-1}^n(n-1) d x \\
& =1+2+3+\ldots .+(n-1)=\frac{(n-1) n}{2}=66 \\
& \Rightarrow n(n-1)=132 \Rightarrow n=12
\end{aligned}\)
Asked in: BITSAT 2009
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