Question

Find the sum of series 4+9+14+......+154

Answer 1

The given sequence forms an arithmetic progression.

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

a=4 , d=9-4=5

General term= a+d(n-1)

154=4+5(n-1)

150=5(n-1)

30=n-1

n=31

Sum= 31/2 (2*4 + 5 ( 31 - 1))

= 31/2 (8 + 5* 30)

= 31/2 * 158

= 2449 // Answer

Answer 2

Answer:=2449

Step-by-step explanation:

a=4

d=5

a_{n}=154

a_{n}=a+(n-1)d

154=4+(n-1)5

154=4+5n-5

154=5n-1

5n=154+1=155

n=155/5=31

s_{n}=n/2(a+a_{n})

       =31/2(4+154)

        =31/2×158

       =31×79

= 2449