Principal, 2000$; Annual interest rate, 5.5%; time, 4 years

simple interest

formula = PRT/100

P = 2000$

rate = 5.5%

time = 4 years

= 2000  x 5.5 x 4 / 100

= 440$

amount = S.I. + P

= 2000 + 440

= 2440

compound interest

formula for amount = P( 1 + r/100 )^n

= 2000( 1 + 5.5/100 )^4

= 2000 (100/100 + 5.5/100)^4

= 2000 ( 105.5/100 )^4

2000 x 105.5/100 x 105.5/100 x 105.5/100 x 105.5/100

= 2 x 105.5 x 105.5/10 x 105.5/100 x 105.5/100

= 211 x 105.5/10 x 105.5/100 x 105.5/100

= 2215.5  x 105.5/100 x 105.5/100

= 2,454.22

compound interest = A - P

= 2454.22 - 2000

= 454.22

x=30

step-by-step explanation:

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.