Question

Find the sum of all multiples of 7 line between hundred and thousand

Answer 1

Answer:

70,336

Step-by-step explanation:

A.P.=105,112,119,.........994

a=105 d=7 an=994

an= (a+(n-1)d)

994=(105+(n-1)7)

994-105=7n-7

889=7n-7

889+7=7n

896=7n

n=128

Sn=n/2 (2a+(n-1)d)

S128=128/2 (2 (105)+(128-1)7)

S128=64 (210+(127)7)

S128=64 (210+889)

S128= 64 (1099)

S128=70336