Question

if the sum of first five term of an A.P. 8s 30 and the sum of first four terms is 20 then the 5th term of the A.P. is??
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Answer 1

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Answer 2

Sum of first five terms=30

Sum of first five terms=n/2(2a+(n-1)d)

30=5/2(2a+4d)

60=10a+20d

6=a+2d(divide 10)

a+2d=6........(i)

Sum of first 4 terms=2(2a+3d)

20=4a+6d

10=2a+3d(divide by 2)

2a +3d=10.....(ii)

Multiply i by 2

2a+4d=12..(i)

Subtract i and ii

2a+3d=10

- 2a+4d=12

-d=-2

d=2

put d=2 in (i)

2a+4(2)=12

2a=12-8

2a=4

a=2

5th term=a+4d

=2+4(2)

=2+8

=10