Question

In AP a10=20,a20=10 find a30

Answer 1

a10=20

so

a + (n-1)d = X

so as the term is 10th

so put n=10

now, a + 9d = 20

for n=20

a + 19d = 10

Now subtract both equations

10d = -10

so, d = -1

now put value of -1 in any of the two equations above

so,

a - 9 = 20

so,

a= 29

now to find a30

a + 29d = X

so, 29 -29 = X

so X=0

ANSWER = 0