Question 1

If $$A = 1 - 10 + 3 - 12 + 5 - 14 + 7 + …$$ upto 60 terms, then what is the value of $$A$$?

Solution

$$A=1-10+3-12+5-14+7+\dots..upto\ 60\ terms\ .$$

or, $$A=\left(1+3+5+7+...59\right)-\left(10+12+14+....+68\right)\ .$$

or, $$A=\frac{\left(1+59\right)\times30}{2}-\frac{\left(10+68\right)\times30}{2}\ .$$

or, $$A=900-1170\ =-270\ .$$

D is correct choice.

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