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MathsHardMCQ2014 ยท 09 Apr Online

Q66.If the sum 3 + 5 + 7 + .... .+ up to 20 terms is equal to 21k , then k is equal to 12 12+22 12+22+32 (1) 240 (2) 120 (3) 60 (4) 180

What This Question Tests

This question requires identifying the general term of a series, simplifying it using the formula for the sum of squares, and then finding the sum using the telescoping series method, potentially requiring inference for a numerical constant.

Concepts Tested

General term of a seriesSum of squares of natural numbersPartial fractionsTelescoping series

Formulas Used

ฮฃr^2 = r(r+1)(2r+1)/6

1/(r(r+1)) = 1/r - 1/(r+1)

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