Question

1. The sum of first ten terms of the A.P 15,
10,5, ........ is .....​

Answer 1

Answer:

75 is your answer.

Step-by-step explanation:

a=15, d{common difference}=a2-a1=10-15=-5, n=10

Sn=n/2{2a+{n-1}d}

=10/2[2{15}+{10-1}{-5}]

=5 x {30-45}

=5 x {-15}

=75.

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Answer 2

Answer:

by using formula

n/2(a+(n-1)*d)

10/2(10+(10-1) *-5)

5(10+9*-5)

5(10-45)

5*-35

-175 Answer