Question

evaluate the following pattern.

31 + 32 + 33 + ____+40

( ans 355 )

explain it....

Don' t give irrelevant answer..​

Answer 1

Answer:

$1 + 2 + 3 + .... + n \: = \frac{n(n + 1)}{2}$

Therefore

31 + 32 + 33+...... +40

= (1+2+3+....+40) - (1+2+3+....+30)

= 40(40+1)/2 + 30(30+1)/2

= 820 - 465

= 355