Given that 6,9,13½,21/4,form a sequence of number. Find the sum of the 13th term

Answer 1

If the pattern is correct, your 4th term should be 20 1/4 or 20.5 , not 21/4
looks like a GS, with a = 6 and r = 1.5

sum(13) = a( r^13 - 1)/(r-1) = 6(( 3/2)^13 - 1)/(3/2 - 1)
= 6(1594323/8192 - 1)/ (1/2)
= .....

Answer 2

Yes