Total time = upstream time + downstream time
he rowed the same distance both ways.
upstream time = D/4
downstream time = D/6
total time = D/4 + D/6 = 3D/12 + 2D/12 = 5D/12 = 3 hours
D = 3*12/5 = 36/5 or 7.2 miles
where D is the one-way distance. The total distance he rowed is 2*D = 72/5 or 14.4 miles
Common ratio = 8/2 = 32/8 = 4
10th term = a1*r^(n - 1) where a1 = 2 , r = 4 and n = 10
= 2 * 4^9
= 524,288
