Kalvin's mother tells him that the chance of a coin showing heads when he tosses it is 1/2. does this mean that every time he tosses a coin twice, he will get one head and one tail.

No it is not necessary that Kelvin will get one head and one tail every time

Explanation:

Probability in math is equal to favorable outcomes/total outcomes

The coin has two sides a head and a tail. When we flip a coin we have 50-50 possibility of getting a head and a tail. It means with every toss we have 1/2 possibility of getting head as well as tail.

But this does not mean that when we toss a coin twice we will get one head at one toss and one tail at another toss.

There is a possibility of getting both heads as well as both the tails.

step-by-step explanation:

12: 00 p.m. to 7: 00 p.m. is a total of 7 hours.

4: 00 p.m. to 7: 00 p.m. is a total of 3 hours.

this means that from 4: 00 p.m to 7: 00 p.m. this represents 3/7 of what was lost from 12: 00 p.m. to 7: 00 p.m.

after knowing this, after doing 11,600 - 6,800 = 4,800

4,800 represents 3/7 of what was lost for 7 hours.

we then divide 4,800 by 3 which gets 1,600.

because we know that 1,600 represents 1/7 of how much water was lost, we just have to multiply by 7, which gets 11,200.   after adding 11,200 to how much water was left at 7: 00 p.m. which was 6,800. 11,200 + 6,800 = 18,000

this means that the pool originally had 18,000 gallons in the pool.

you can also check your work by doing 18,000 - 4(1600), which becomes           1800 - 6400 which gets you 11,600.