Question

25+28+31+.......+100 =
1) 1624
2) 1625
3) 1525
4) 1342​

Answer 1

Answer:

Step-by-step explanation:

a= 25  

d =28 - 25 = 3

an = 100

an = a+( n - 1) d

100 = 25 + (n-1) (3)

100 -25 = (n-1) (3)

75= (n-1) (3)

75/3 = (n-1)  

25 = (n-1)  

25 +1 = n  

26 = n

Sn = n/2 (a +an)

    =  26/ 2 ( 25 +100)  

      = 13 ( 125 )

     = 1625  

     

Answer 2

Answer:

25+28 +31+1500+100=1624