Question

please explain it in detail

Answer 1

The sum of n consecutive odd numbers =
${n}^{2}$
So 1+3+5+7+9+11+13
has 7 numbers hence n=7
sum will be
${n}^{2} = {7}^{2} = 49$
Now for finding sum of 15+17+19+21+23+25

Find the total sum of odd numbers till 25 I.e 1+3+5------+25
=n=13
the sum will be
${13}^{2} = 169$
Now for find the sum of 15+17+19+21+23+25=
sum of (1+3+5+7----+25)-sum of (1+3+5+7+9+13+15)
=169-49=120
hope this helps you...