Question

find the sum of all multiples of 5 lying between 101 and 999

Answer 1

ap.is 105 ,110 ,115 ..........995
first by formula
an = a + ( n-1) d find nterm
995 = 105+(n-1) 5
995= 105+5n-5
995-100= 5n
5n = 895
n = 895/5
n = 179
now by formula
sn = n/2 {2a+(n-1) d}
sn = 179/2{2×105+(179-1)5}
sn= 89.5{210+ 890}
sn= 89.5+1100
sn = 1189.5
I think it is right .........

Answer 2

Answer:

The answer is in the attachment. Please mark me as brainiest. x