To solve this problem we will start by calculating time needed for each of them to fill the pool.
We have formula:
Volume = rate * time
Or
time = volume / rate
Wilma:
time = 9900 / 900
time = 11h
Betty:
time = 9900 / 500
time = 19.8h
Now we substract these two numbers:
time_difference = 19.8 - 11 = 8.8h
Betty needs 8.8 hours more than Wilma to fill the pool.
When you divide 6x10^24 by 8x10^8 you end up with 
This simplifies to 
Now this number is not written in scientific notation as it does not have its first digit before the decimal, so we must move the decimal of this one to the right.
To do that you must multiply the number by 10.
This means that the exponet of 10 must decrease by 1.
This makes the answer 
Answer:
Choice B & C
Step-by-step explanation:
563 - 192 = 371
The subtraction equals to 371.
100 + 90 + 210 = 400
The answer does not equal to 371 in choice A.
563 - 200 + 8 = 371
The answer equals to 371 in choice B.
571 - 200 = 371.
The answer equals to 371 in choice C.
Step-by-step explanation:
4) y²-1=48
y²=49
y=±7
option C -7 and 7
5) x²=289
x=±17
-17 and 17