Question

If the sum of a1 + a10 = 50 for an A.P. Find the value of a1 + a2 +…… + a10?

Answer 1

Answer:

900

Step-by-step explanation:

We know,

an= a + (n-1)d.

So according to it,

a1+a5+a10+a15+a20+a24=225 can be written as:

a+a+4d+a+9d+a+14d+a+19d+a+23d=225

6a+69d=225…..(1)

Now sum of AP series is:

Sn=n/2[ 2a+(n-1)d]

so, S24= 12[2a+23d] (n=24)

Now , mutiplying and dividing by 3.

s24= 12\3[6a+69d]

From eq1 ;

s24= (12\3)*225

S24=900.

Ans=900.

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Answer 2

answer: the sum is 250

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