Question

Calcular: 11+21+31+41+.…..+151

Answer 1

Calcular: 11+21+31+41+.…..+151

hallamos la razon

r = 21 - 11

r = 10

hallamos el numero de terminos

n = $\frac{tn - t1}{r }$  + 1

n = $\frac{151 - 11}{10}$ + 1

n = $\frac{140}{10}$ + 1

n = 14 + 1

n = 15

ahora hallamos la suma

S = 11+21+31+41+.…..+151

S = ($\frac{t1 + tn}{2}$ )n

S = ($\frac{11 + 151}{2}$ )10

S = ($\frac{162}{2}$ )10

S = (81)10

S = 810