maths
posted by Amir khan on .
1) The first term of arithmetic progression is 20 and the sum of it's term is 250. find it's last term if the number of it's terms is 10
2) Find the fifth term from the arithmetic progression 12, 9, 6 hence find the sum of it's first fifty terms.
3) The sum of the first terms in Arithmetic progression is equal to 24, and the sum of the last six terms equal to 30. if the number of it's term is 12. find a) it's common different
b) The first term
c) the last term

Answer

3)a=12
d=3
t(5)=a+(n1)d
=12+(51)3
=0
s(50)=3625
hope it would be a help. :) 
U2= a=8/9 U2=8/9 Un= arn1 if n=2 U2= arn71 8/9=2(r6)

1) a=20
Sn=250
. n=10
Sn=n/2(2a+(n1)d)
250=10/2(2(20)+(101)d)
250=5((40)+(9)d)
250=200+45d
250+200=45d
d=10
Un=a+(n1)d
Un=20*(101)10
Un=20+900
Un=880
::the last term=880 
2) a=12
. Un=6
d=3
n=5
S5=5/2(2(12)+(51)3)
2.5(24)+12)
. 2.5(36)
S5=90