Question

Find the sum 32 + 30 + 28 + .................... + 10.

Answer 1

Here, $$a = 32, \ d = -2, \ l = 10$$. 

$$32 + (n - 1)(-2) = 10$$

$$\Rightarrow n = 12$$ 

$$S_{12} = \frac{12}{2}(32 + 10)$$

$$= 6(42)$$

$$= 252$$