can u help me with this complicated math assignment?

Question

the sand on a beach is being washed away by slowly by erosion. in 1870, a lighthouse was 1500 feet from the shoreline. in 1990, the lighthouse was only 150 feet from the shoreline. if the erosion continues at this rate, how many years will it be before the lighthouse is at the shoreline? please if u have the answer, explain it to me..please...

Answer 1

pretty easy ;-)

between 1870 and 1990, you have 120 years.

during those 120 years, the shoreline was eroded by 1500 minus 150 feet, which is 1350 feet.

so the shoreline erodes at a rate of
1350ft divided by 120 years = 11.25 ft / year

the lighthouse is currently 150 feet away from the shoreline. To get to the lighthouse with erosion progressing 11.25 ft / year, you'll need:

150 ft / (11.25 ft/year), which is 13 years and a third.

If you want an answer in whole years only, then that's 14 years because after 13 years you'll still have a bit of shore left.

Hope this helps

a

Answer 2

We see that from 1870 - 1990, which is 120 years, the shoreline has receeded by 1500 - 150 = 1350 feet.

So erosion takes place at the rate of 1350 feet every 120 years. Simplifying that, we find that 120/1350 or 4/45 year passes by for every feet eroded.

Thus to erode 150 feet more, the number of years required would be 150 x 4/45 = 13 1/3 years.

Answer 3

Sure. Its a simple matter of reasoning it out and ratios. Lets look at the information. 1500, 150 in feet. 1990, 1870 in years. How much has all ready been eroded?

1500 ft - 150 ft = 1350 ft
1990 - 1870 = 120 yrs

so it moved 1350 ft in 120 yrs. that can be said as a ratio. 1350/120 ft/yrs... reduce that and we have 11.25 ft per year.

And we only have to move this lighthouse 150 ft. This can be set up as a ratio. What we don't know is how many years it going to take, we'll call that x. so 11.25 ft / 1yr = 150 ft / x yrs.

With a little bit of algebra we have x yrs= 150 / 11.25 yrs (the feet cancel out- its a good habit to always label your work. that way you know what number is what. ) With a little division, we have x = 13 1/3, or 13 years, 4 months (4 months is a 1/3 of the year)

Anyways, hope this helps

Answer 4

150 feet is 10% of the original 1500 feet so in 120 years 90% of the beach was eroded. 1350 feet have eroded in 120 years.

At that rate, consider that every year about 13 feet of the beach is eroded. (1350 divided by 120) So it will take about 11 years (150 divided by 13) for the lighthouse to be at the shoreline. You will need to do the math to get the exact answer. I hope this helps.

Answer 5

In 1870 it was 1500 ft
in 1990 it was 150 ft

1990 - 1870 = 120 years
1500 - 150 = 1350 ft

Therefore it has eroded 1,350 ft in 120 years
so for 150 feet how many years:

(150 * 120)/1350 = 13.33 years

or to be precise in days

(150*120)/(120*365) =4,866.66 days

Answer 6

Basic ratios and rates. It dropped 1350 feet in 120 years. so 1350/120 = 150/x. x=13 1/3

Answer 7

I can help you, but I'll let you do the actual work! If you figure out how many years it is from 1870 to 1990, and then figure out how much the distance has diminished, you will be able to find the 'yearly' amount of change by dividing the distance by the time. Then just figure how long it will take (at that yearly rate) to "use up" what distance is left!

Answer 8

1990-1870 years have elapsed. (x)
There's a difference of 1500-150 feet. (y)

Therefore y feet in x years.

So to get how long it takes for 1 foot, you divide y by y to get 1, and x by y to get the time it takes.

e.g y/y = 1 x/y = time to erode one foot.

Then as you want to know how long it will take to erode 150 feet:

x/y multiplied by 150.

And that's your answer.

Answer 9

1500 ft original - 150 ft current = 1350 ft eroded since 1870

1350 ft divided by 120 year (1990 - 1870) = 11.25 ft eroded per year
150 ft remaining divided by the rate of erosion 11.25 ft per year =
13.33 year

Answer 10

hmmm.....the answer maybe 13.3 yrs

if it took 120 yrs to reduce by 1350 meters...then each yr it reduces by about 11.25 meters. So for a further 150 meters it wiill take about 150/11.25 = 13.3 yrs

It shot in the dark......but i am just trying...hope it is right