C, because the opposite would be + 2 and none of the ions have that charge
Lets call the rate at which the first panel absorbs solar energy x:
x = 9/7
To find out how much energy the panel will absorb in a certain number of hours, just multiply x by the time:
In 7 hours, energy = (9/7) * 7 = 9MJ
In 8 hours, energy = (9/7) * 8 = (72/7)MJ
Let's call the rate at which the second panel absorbs solar energy y. Therefore, we can write an equation, in x and y, using the information in the question:
5x + 5y = 41
We know what x is, so 5x = 5 * (9/7) = (45/7):
(45/7) + 5y = 41
5y = 41 - (45/7)
41 is the same as (41*7)/7 = 287/7:
5y = 287/7 - 45/7 = (287-45)/7 = 242/7
Divide both sides by 5 to find the value of y (in MJ absorbed per hours, MJ/h):
y = 242/35 = 6.914285714MJ/h
Let's call the time taken for the new panel to absorb 41MJ t:
ty = 41
We know what y is, so substitute that in and solve:
6.914285714t = 41
t = 41/6.914285714 ≈ 5.929752066 hours
I would like to express this value in the SI unit, which is seconds, s:
5.929752066 * 3600 = 21347.1s
X - S<span>arah's age now
3x - </span><span>Ralph is 3 times as old as Sarah, now
x+6 - </span>Sarah's age in 6 years
2(x+6)=2x+12 - R<span>alph will be only twice as old as Sarah will be in 6 years
</span>Ralph's age in six year can be also written as 3x+6<span>
So
</span>Ralph's age now is 3x.
Ralph's age in six years is 2x+12 and 3x+6.
We can find age of Sara now,
2x+12=3x+6
3x-2x=12-6
x=6,
Ralph's age now is 3x=3*6=18
Now Sara is 6 years old, Ralph is 18 years old.
The answer to your question is 3.6
