Answer:
2 hours
Step-by-step explanation:
Let x mph be the speed of motorboat in still water and y mph be the speed of current.
A raft and a motorboat simultaneously leave from the same point and move down the river, then speeds down the river are:
motorboat = x + y mph
raft = y mph
In two hours they will cover:
motorboat = 2(x+y) miles
raft = 2y miles
After 2 hours the motorboat turns around and starts moving towards the raft (against the current), so its speed is now x - y mph.
Let t be the time they move towards each other. In t hours, they cover
motorboat = t(x - y) miles
raft = ty miles
The distance from the starting point to the turning point is the same as the sum of the distances the raft covers and the motorboat covers after turning around, so
Let's use the "elimination by addition/subtraction" method to solve this system for x and y.
<span> -8x=72-16y
4x=-92+16y <= Mult. all 3 terms by 2: 8x = - 184 + 32y
Now combine the following, column by column:
</span><span> -8x= 72-16y
</span>8x = - 184 + 32y
-----------------------
0 = -112 + 16y. Solving for y, 16y = 112, and y = 7.
Now subst. 7 for y in either of the original equations and calculate x:
<span>4x=-92+16(7) => 4x = -92 + 112 = 20. Then x = 5.
Solution is 5, -7 (or, better written) (5, - 7).</span>
Answer:
B.
Step-by-step explanation:
i think its right
The formula of the future value of annuity ordinary
Fv=pmt [(1+r)^(n)-1)÷r]
Fv future value
Pmt payment per year 4000
R interest rate 0.0215
N time 5 years
Fv=4,000×(((1+0.0215)^(5)−1)÷(0.0215))
fv=20,878.69
I think that the answer is 120 cubes
