Answer:
Explanation:
One of the applications of scientific notation is to make estimations rounding the whole part of the numbers, i.e. the digits before the decimal point, to the nearest integer, and adding the exponents of the powers of base 10.
Here, you must estimate this product of two numbers written is scientific notation:
Then, for an estimation you round 3.21 to 3 and 1.13 to 1, then multiply 3 × 1 = 3. That will be the coefficient of your new power of 10.
The power or exponent will be the sum of the powers of the numbers that are being multiplied, i.e. 3 + 5 = 8.
And the result is 
The unit is meters, so you write your answer as: 
I cannot see Zoe's work to explain the error, but the correct method of solving is listed:
x is the number of 30-second ads
y is the number of 60-second ads
x+y=12(60)=720 would be the first equation; this is because while the ads together make 12 minutes, the ad times are in seconds. This means we must multiply 12 by 60.
y=2x is the second equation
Our system is then
x+y=720
y=2x
We will use substitution to solve this. Plug 2x in place of y in the first equation:
x+2x = 720
Combine like terms:
3x = 720
Divide both sides by 3:
3x/3 = 720/3
x = 240
Substitute this value in for x in the second equation:
y=2(240)
y=480
S = d/t
st = d
t = d/s
The time going is t1.
The time returning is t2.
The total time is 4 hours, so we have t1 + t2 = 4
The speed of the current is c.
The speed going is 9 + c.
The speed returning is 9 - c.
t1 = 16/(9 + c)
t2 = 16/(9 - c)
t1 + t2 = 16/(9 + c) + 16/(9 - c)
4 = 16/(9 - c) + 16/(9 + c)
1 = 4/(9 - c) + 4/(9 + c)
(9 + c)(9 - c) = 4(9 - c) + 4(9 + c)
81 - c^2 = 36 - 4c + 36 + 4c
81 - c^2 = 72
c^2 = 9
c^2 - 9 = 0
(c + 3)(c - 3) = 0
c + 3 = 0 or c - 3 = 0
c = -3 or c = 3
We discard the negative answer, and we get c = 3.
The speed of the current is 3 mph.
Answer:
-5 / 8 - -4 / 8 equals the approximate estimate notation of 58.7
Well, he made $100 off of drinks, and $135 off of ice cream bars.
Then to find his profit take $235 - $31.50 = $203.50
There's your answer! $203.50 was his profit.
