Question

Find the value of x when in the A.p given below 2+6+10+.......+x=1800
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Answer 1

Answer:

Answer is 118

Step-by-step explanation:

sum of n terms in an A.P= n/2[a + (n-1)d]= n/2[a + l] where l is the last term of the AP

here, a = 2 d= 6-2=4 Sn= 1800 an=x=l

an= a+(n-1)d=2+(n-1)4= 2+4n-4=4n-2

Sn= n/2[a + x]=n/2[2+4n-2]=n/2[4n]=2n^2=1800

n^2=900

n=30

x= 4n-2=4×30-2=120-2=118