Answer:
2.06×10^14
Step-by-step explanation:
nth term of G.p = ar^n-1
the first term, a = 3 common ratio, r = 2nd term/ 1st term, 3rd term/ 2nd term, etc.
r = 9/3 = 3
30th term = 3(3)^30-1 = 2.06×10^14
Answer:
Speed of boat in still water is 6km/h
Speed of current is 4km/h
Step-by-step explanation:
We know speed = distance / time
Let the speed of boat in still water be x
Let the speed of current be y
Hence the speed of boat, down stream = 
Distance downstream = 20km
Time taken = 2 hours
We have

......(1)
Speed of boat upstream = 
Distance upstream = 4
Time taken = 2
We have

...(2)
Adding (1) & (2)


Substituting in (1) we get

Answer is a right triangle. The angles of a triangle must add to 180 degrees.
You have two 45 degree angles
45 + 45= 90
Now you need 1 more angle to equal 180
180- 90= 90
A right angle is 90 degrees. A right triangle has one right angle and two acute.