Try to put the numbers 1 to 12 in the twelve boxes below so that the numbers along each side add to 26.

We have to arrange different numbers ranging from 1 to 12 in each boxes such that the sum along each of the side is equal to 26.

In the first row we arrange the numbers as:

  8   9   3   6

( since, 8+9+3+6=26)

In the last row we write the numbers as:

  5    10   4   7

( since, 5+10+4+7=26)

In the first column we arrange numbers as:

   8

    1

   12

    5

( Since, 8+1+12+5=26 )

In the last column we arrange numbers as:

    6

    11

    2

    7

( Since, 6+11+2+7=26)

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.