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← JEE Main 2022 · 28 Jul · Shift 1
MathematicsInteger+4 / -1Question 28 of 90

JEE Main 2022 · 28 Jul · Shift 1, Mathematics question 28

Let x1,x2,x3,…,x20x_1,x_2,x_3,\ldots,x_{20} be in geometric progression with x1=3x_1=3 and the common ratio 12\dfrac12. A new data is constructed replacing each xix_i by (xi−i)2(x_i-i)^2. If xˉ\bar x is the mean of new data, then the greatest integer less than or equal to xˉ\bar x is ______.

Answer and worked solution

Official answer: 142

Mean 120∑(3⋅21−i−i)2≈142.9\frac1{20}\sum\left(3\cdot2^{1-i}-i\right)^2\approx142.9.

Answer: 142