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The sum '5 + 6 + 7 + 8 + ............ + 19' is equal to :
- A150
- B170
- C180
- D190
Answer not set
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0
CCommunity
option 3 is the answer
0
CCommunity
1 + 2+3 +.... +n= $\frac{n(n+1)}{2}$
5 + 6 + 7 + .... + 19
= (1 + 2 + 3 + .... + 19) – (1 + 2 +3 + 4)
$\frac{19(19+1)}{2}-10$ = 180
5 + 6 + 7 + .... + 19
= (1 + 2 + 3 + .... + 19) – (1 + 2 +3 + 4)
$\frac{19(19+1)}{2}-10$ = 180