Question

in an AP a=-10 and a20=250, find s20

Answer 1

Answer:

a =-10

a20=250

a+19d=250

sub a = -10

-10+19d=250

19d=250+10

19d=260-----(1)

s20=n/2(2a+(n-1)d)

s20=20/2(2*-10+(20-1)d)

=10(-20+19d)------(2)

sub (1) in (2)

=10(-20+260)

=10(240)

=2400

Step-by-step explanation:

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