Question

iii 1 + 2 + 3 + ... + 14 + 15 + 16
Work out a way to apply the shortcut w​

Answer 1

Answer:

120

Step-by-step explanation:

Lets assume the sum of the sequence as S1

S1 = 1+2+3..+15+16

and a sum of the same sequence but in the reverse order as S2

therefore,

S2 = 16+15+14..+2+1

S1 + S2 = 17+17+17+17..+17

implies that

2S1 = 17+17..+17

=2S1 = no×17 (no is the number of terms)

=S1 = 1/2 × no×17

or

S1 = 1/2×no×(First term + Last term)