CBSEi Class 10 Sequences (AP and GP) CORE
CBSEi Class 10 Sequences (AP and GP) CORE
CBSEi Class 10 Sequences (AP and GP) CORE
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2. Write the formula for the sum of first n terms of an A.P.<br />
S3 = a1 + ( a1 + d) + ( a1 + 2d) = 3a1 + 3d<br />
= 3/2[2a1 + (3-1)d]<br />
S4 = 4a1 + 6d<br />
= 4/2[2a1 + (4 − 1)d]<br />
S5 = 5a1 + <strong>10</strong>d<br />
=5/2[2a1 + (5 − 1)d]<br />
Sn =<br />
3. Observe the given pattern <strong>and</strong> answer the questions.<br />
1= 1=<br />
1+2 = 3 =<br />
1+2+3 = 6=<br />
1+2+3+4 = <strong>10</strong> =<br />
What will be the sum of first n terms?<br />
What will be the sum of first <strong>10</strong>0 terms?<br />
4. Find the sum of first <strong>10</strong> terms of an A.P. whose nth term is 2n+3. What strategy<br />
did you apply?<br />
<strong>10</strong>8
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