Ryan S. answered 06/10/16
Tutor
New to Wyzant
Mechanical Engineering Major
First off we need to set some variables.
Let's let C = number of carts and N = the number of carts that are inside another cart. N will just be C - 1 since the cart on the end of the row cannot be in another cart since it is on the front of the row.
Scroll down to page 8 of this PDF to see a picture of the setup.
http://www.nps.k12.nj.us/SCI/wp-content/uploads/sites/67/2015/06/Rising-8th-Graders-or-Entering-Algebra-I.pdf
Now on to part a).
How long would a row of carts be if they were not nested? 3 ft x 12 carts = 36 ft.
How long is the row with nested carts? 16.75 ft (this is a given).
What's the difference in the two measurements? 36 - 16.75 = 19.25 ft. The nested row is 19.25 feet shorter. When we divide this by the 11 nested carts we will find out how much each cart is in another cart. 19.25/11 = 1.75 ft.
Each cart is 1.75 feet inside another cart.
Now on to part b).
First find the length of an un-nested row: 20 carts x 3 ft = 60 ft.
Now multiply the 1.75 feet we got earlier by the number of carts there are minus 1: 1.75 x (20 - 1) = 33.25. This number is the amount of cart nested in another cart totaled.
Now subtract this number from 60 to get 60 - 33.25 = 26.75 ft. This is the row length of 20 nested carts.
Part c): Do this after finishing part d) since d) is easier.
Part d): We let C = the number of carts earlier and we let N = C - 1. We let L be the total length of the row.
Notice what we did in part a), we subtracted the 1.75 x N from 3 x C to get L.
In equation form this is: 3C - 1.75N = L or 3C - 1.75(C - 1) = L. Simplified this is: 1.25C + 1.75 = L.
This is the equation: 1.25C + 1.75 = L.
Part c): Just solve for C. 1.25C + 1.75 = 34.25 ==> 34.25 - 1.75 = 1.25C ==> C = 26 carts. You need 26 carts.
Part e): This part is a little bit of trial and error. Remember, you cannot only part of a cart and you cannot have a row that is longer than 50 feet long. The best thing to do is try guessing a number of carts and plug it into the equation from part d).
Let's try C = 30 carts: 1.25 x 30 + 1.75 = 39.25 feet long. That's good, but we can probably put more carts in there. Let's try C = 40 carts: 1.25 x 40 + 1.75 = 51.75 feet long. That's too long. Our answer is somewhere between 30 and 40 carts. Let's try 38 (because I did it for you and it's 2 carts fewer, which should yield a slightly smaller number).
C = 38 carts: 1.25 x 38 + 1.75 = 49.25. This is right near the edge. You cannot fit any more carts in a single row than this. Since there are 3 rows multiply the 38 carts in one row by 3 to get a total of 114 carts in 3 rows. You can keep 114 carts inside.
Part f): Since there are 200 carts and 114 of them can stay inside, how many are outside?
200 - 114 = 86 carts outside at night.
There you go.
Hope this helps!
Edit: For the equation we made in part d), C should be n since that is how the question wanted the answer. This means the answer for d) should be 1.25n + 1.75 = L. The same holds throughout the rest of the problem answer.