Question

What i sthe value of 2+4+6+....+80 is

Answer 1

Answer:

Using Simple logic  

To sum up this series

2+4+6+8+...+80

Take 2 common, so you will get

2(1+2+3+4+...+39+40)  

We know the formula for sum of continuous series that is  n(n+1)/2  

=2(n(n+1)/2)  

=n(n+1)  

=40(41)  

=40×41=1640

Sum of this series is  1640

Answer 2

Answer:

1640

Step-by-step explanation:

an = a+ (n-1)d

80 = 2 + ( n-1 ) 2

80 = 2+ 2n -2

80 = 2n

n = 40

Sn = n/2 [ a + an ]

Sn = 40/2 [ 2 + 80 ]

Sn = 20 × 82

Sn = 1640

Final answer -

1640

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