Question

1+2+3+4...+98+99+100 EXPLICATI VA ROG FRUMOS

Answer 1

100(100+1):2 = (100x101) :2 =5050

Answer 2

$\displaystyle 1+2+3+4...+98+99+100=? \\ \\ \boxed{ \frac{n(n+1)}{2}} \\ \text{Formula prin care rezolvam sirul.} \\ \text{n=ultimul numar din sir.} \\ \\ \frac{100(100+1)}{2} = \frac{\not100\cdot101}{\not2} = 50 \cdot 101= 5050$