Question

For an Ap 1 upon 6. 1 upon 4. 1 upon 3 find 15th term and sum of first 10 terms

Answer 1

Answer:

AP 1/6,1/4,1/3.....

d=t2-t1= 1/4-1/6=3-2/12=1/6

a=1/6

an = a+(n-1)d (n=15)

a15 = 1/6 +(15-1)1/6

1/6+7/6

1+7/6 = 8/6=4/3

A15=4/3

the sum is (n=10)

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

S10=10/2{2*1/6(10-1)*1/12}

5{1/3+9*1/12}

5{1/3+3/4}

5{4+9/12}

5{13/12}

65/12

S10=5.42