Given:
The sum of two terms of GP is 6 and that of first four terms is 
To find:
The sum of first six terms.
Solution:
We have,


Sum of first n terms of a GP is
...(i)
Putting n=2, we get


...(ii)
Putting n=4, we get



(Using (ii))
Divide both sides by 6.
Taking square root on both sides, we get

Case 1: If r is positive, then using (ii) we get
The sum of first 6 terms is




Case 2: If r is negative, then using (ii) we get
The sum of first 6 terms is




Therefore, the sum of the first six terms is 7.875.
Answer:
i believe it would be the last option.
Step-by-step explanation:
Answer:
112.5 mL
Step-by-step explanation:
Let x represent the amount of grape juice to add. Then the total amount of grape juice in the mix is ...
0.15(1800) +x = 0.20(1800+x)
270 +x = 360 + 0.2x . . . . . . eliminate parentheses
0.8x = 90 . . . . . . . . . . . . . . . subtract 270+0.2x
x = 90/0.8 = 112.5 . . . . . . . . divide by the coefficient of x
112 mL of grape juice should be added to make a mix that is 20% grape juice.
Thw answer is X = 3 or -3