Problem 2

Crossing The Desert

A traveler undertakes to walk, alone and without help, across a desert entirely lacking in resources. Every 20 kilometers on the 100 kilometer trail there is a shelter. (20 kilometers is exactly what a traveler can walk in one day.) The traveler can only carry 3 days' food. He can stock food only in shelters. How many days will it take him to cross the desert? — Mr. Simmons

Your Thoughts…


i think 11 days and i'll explain later

Day 1: Travel to 1rst shelter with 3 days of food and eat one day and store two days of food


Its 15 days…It can't be 11 days Rohan
Day 1: he starts out with 3 days of food. He got to shelter 1. He stores 1 day of food at shelter 1.
Day 2: He goes back to get another 3 days of food. So far he is at the 0km mark and has stored 1 day of food at shelter 1.
Day 3-6: He repeats this process 2 more times, and doing that we get him back at the 0km mark after 6 days and has stored 3 days worth of food at shelter 1.
Day 7: Next, he goes to shelter one, restocks his food,
Day 8: Goes to shelter 2, he stores one meal there
Day 9: Goes to shelter 1
Day 10: Then goes back to the starting point. This leaves our traveler at the 0km mark after 10 days with 2 meals at shelter 1 and one meal at shelter 2.
Day 11: He goes to shelter 1, restocks
Day 12: Goes to shelter 2, restocks, leaving him at the 40 km mark after 12 days with 3 days worth of food. At that point, he can finish the trip without going back.
Day 13: Shelter 3: 2 days of food left
Day 14: Shelter 4: 1 day of food left
Day 15: 100km mark, he reaches his mark and wonders why he didn’t just fly in a plane

Sorry it gets kinda hard to explain…if you don't understand, tell me…

or u can look at it this way…look at the chart below from the editing screen…it looks awkward from the actual view…

Day #ofpacks S1 (20) S2(40) S3(60) S4(80) S5(100) Current Position
1 1 1 X X X X Shelter 1
2 3 1 X X X X Home
3 1 2 X X X X Shelter 1
4 3 2 X X X X Home
5 1 3 X X X X Shelter 1
6 3 1 0 X X X Shelter 2
7 1 1 1 X X X Shelter 1
8 1 0 1 X X X Home
9 3 0 1 X X X Shelter 1
10 1 1 1 X X X Home
11 3 1 1 X X X Shelter 1
12 3 0 1 X X X Shelter 2
13 3 0 0 0 0 0 Shelter 3
14 2 0 0 0 0 0 Shelter 4
15 1 0 0 0 0 0 Shelter 5


Madhula A.

I think ur wrong- here is why-

day 1- Travel to 1rst shelter with 3 days of food and eat one day and store two days of food
day 2- go back to 0 mark and get three days worth of food more
day 3- go to shelter 1- and store 2 days worth of food (after eating 1 day---------------------



So he has to go back home to get more days of food….Is that legal? … so just to go back home form the 20km mark it'll take him 2 days…. ahh I see .. i think Madhula is right, because Rohan ..a person has to eat everyday right? i agree with Madhula, but fr some reason i think it could be shorter.. i'm going to see if it can…
♪ Henry Chou ♪

I agree with Madhula :D I think it's 15 days too.
And Rohan, the person can't store 2 days of food on day 1 because he/she has to eat one day of food on the way to the shelter and another day of food on the way back when he goes back to the starting point on day 2. So yah, I think Madhula did it right…
-Mai I.

i know- that was the problem with my answer- i agree with madhula
- rohan k

-but atleast i wasn't looking at the problem wrong like last time

Guys, yall (ahem, Mr. Simmons, wink, wink, ahem WINK WINK WINK!) might be missing something and therefore overanalyzing. Does the guy really need to eat one day's worth of food in one day? he could always skip a day, meaning he would eat the 1st day, skip the 2nd day, eat the 3rd day, skip the 4th day, and eat the 5th. Or, he could eat 3/5 a day's worth of food in one day (3/5 x 5 = 3), each day. The problem never says you have to eat one day's worth of food in one day! What's wrong with being anorexic? Madhula, your reasoning and answer is right, but it might not be the fewest amount of days it takes (i almost wrote taks xD) the man to cross the desert. If my answer is right, it should only take 5 days to cross the desert. So, to clarify, I say it only takes 5 days to cross the desert, because you don't need to eat one day's worth of food each day. If that is right, you don't need to go back and forth, eating, storing, and more eating. Again, I'm not sure if this is stretching it. I might be right, and I might be wrong. If I'm wrong, yall can "own" me. If I'm right, I'm right. Oh yeah, and who says a traveler has to be a man? Rohan, Madhula, and Henry, yall all put "he" instead of "the traveler" or "he/she" or "the person" as Mai did (good job Mai, you not only contributed, but you didn't specify gender! NICEEEEEE! So, just tell me what yall think!

P.S. - Mr. Simmons, I don't think this problem is realistic. There's bound to be luck in this scenario, whether good or bad. Maybe the food got stolen (by John, Henry, and me), bandits (John, Henry, and me) might have attacked him, wizards (John, Henry, and me) could've taught him how to teleport/apparate, or his brothers (John, Henry, and me) could've have given him some help to speed up his journey. But, if you want to just keep it as a problem, ♫ How could you be so heartless? ♫
- Jonathan Y.

Jonathan if the guy could walk 20 km and eat only a days worth of food I'll be surprised.. beside the point of this is do to be robbed/ helped or attacked etc… its to " A traveler undertakes to walk, alone and without help, across a desert entirely lacking in resources" (can you read? your another rohan) besides… now that you mentioned it.. can he go home to get more food? is it possible…i mean what if he lives in Georgia and he tries to cross the death valley dessert.. i mean i would rather keep going then walk back home to get food…
♪ Henry C ♪

First of all, the last part is meant to be a joke -.- . Plus, 20km a day is about 1.5 km/h (about 1 mph), and that is slow! Second, you need to work on your grammer! "cold" instead of "could", "days" instead of "day's", "illbe" isntead of "i'll be", "attacket" instead of "attacked", "(can u read your another rohan)" (I don't even know what that's supposed to say), and finally, your first and last sentence contradict themselves. "If the guy cold walk 20 km and eat only a days worth of food illbe surprised" and "i would rather keep going then walk back home to get food" contradict each other. And 3/5 a day's worth of food can satisfy you. It's like having breakfast, skipping lunch, and eating dinner (that you can survive on and walk 1.5 km/h for 20km a day). Finally, concentrate on my body paragraph, not the p.s. (what does Georgia and death valley have to do? death valley is in california!) Anyways, what do yall think? 3/5 a day's worth of food each day sound good to you?
- Jonathan Y.

I like 5/5 of meals… and i'm just saying that if his house was at Georgia..then walking back to California would be kind of senseless wouldn't it?And yes i know it was a joke …
♪ Henry C ♪


I think it will take 5 days

Put your name at the end of a post and.. you only have 3 days worth of food … how do u travel 5 days with 2 days of no food…?
♪ Henry C ♪

My answer is that it will take the traveler 5 days because you don't have to eat everyday.
Day1: Eat
Day2: don't eat
Day3: Eat
Day4: Don't eat
Day5: Eat
Also, the problem states that he walks without help. Wouldn't storing food in a shelter be considered help.

P.S. I wouldn't store food because whenever i store food i the fridge someone else usually eats it.
Brad S. OUT!!!

who says it takes five days? 5 days is the the most wrong answer i's has ever heards (pardon bad gramme)
p.s. jonathan, why can't i be a wizard?**

-rohan k. - a fabulous nerd





Rohan, I am sure most people agree with my answer (15 days)…do you still think it is 11? Can you please explain to me how?I mean, you could be right…
And to Jonathan,Amir…please be realistic…the guy can't go ANEREXIC!!! Its a problem, it doesn't have any state of change unless the problem itself says so…I don't the guy will starve himself. I am pretty sure with my answer this time.

1 Using his 3 foods he drops 1 at first shelter and then comes back
2 Comes back home gets 3 more foods
3 Goes to shelter 1 and drops off another food pack so now it has 2 food packs
4 Comes back home gets 3 more foods
5 Goes to shelter one and takes 1 food pack out of the original 2, Now he once again has 3 food packs
6 Go to shelter 2, drop a pack of food there. Now he has 1 pack of food remaining and shell 2 has a pack
7 Come back to shell 1, take the food pack from shell 1. He now has 1 pack of food and shell 1 has no fod
8 Come back home refill and get 3 new packs of food
9 Go to shelter 1 drop a pack of food off there

11 Go to shelter 1 pick up the food there, now the guy has 3 packs and shell 2 has 1 pack waiting for him
12 Go to shelter 2 pick up the food there now he once again has 3 packs
13 Go to shelter 3 which is 60km now he has 2 packs left
14 GO to shelter 4 whicj is 80km now he has 1 pack left
15 Go to Destination

-Madhula A

Hey, uh, I think Madhula's right. Because I think whoever thinks it’s five days is assuming there's food IN the shelter which will get you to five days to cross the shelter. However the problem said there are no resources whatsoever.
If you do it your way, then wouldn't you get something like:

ShelterGetFood ~ ~ day1 (20km)~ ~day2 (20km)~ ~day3 (20 km)ShelterGetFood ~ ~day 4(20 km) ~ ~ day5(20km) = 100 km

which is incorrect because there is no food except for whatever the traveler brings with him. and I think the whole anorexic thing and Georgia/California thing is stretching the problem way too far. and anyways, an anorexic would die in the heat and lack of resources in the desert…

I think Madhula’s right because:
a) Distance to cover = 100 km
b) can stop every 20 km to stock food but there is NO FOOD in the shelters
c) to make it across the desert, the first two shelters must have enough food stocked to make it through the journey
d) to stock a sufficient amount of food in these two shelters, as madhula described, the guy has to keep going back and forth until you have enough food in the second shelter to finish the journey.

And Madhula’s reasoning came up to be 15 days: So yeah, I’m pretty sure she’s right.
-Sathvika R.

Yeah, I agree with Sathvika too. It can't be 5 days because then there's no point to the problem…
And I tried seeing if the person could go across the desert in less than 15 days, but I couldn't come up with anything.
So yup, I think Madhula is right. :)
-Mai I.

OMG!!! Its not right!!! I am wrong!!! One second..i am going to go and check again

ps. Jonathan and Henry, this is not a Algebra IMing page…if you are going to discuss something that has to do with the problem please do so; but you are wasting so much of my reading time (and other ppls')…Don't write stories
-Madhula A

Never mind…iz okay


we're wasting our own time too … and yes.. Madhula your reasoning seems to be right.
♪ Henry C ♪

It never says if he has to stop a whole day to stock up on food
-Mark Li
But it says it takes him a day to walk assume that he walks a day stock and sleeps and repeat next day.
☼ Henry C ☼

I probably didn't read it right again. Like the last problem we did but when does it say that he goes home? Some of you guys are saying he is going home. Why can't he sleep and then continue his journey crossing the desert?'

-David G.

Okay… The person has to go home to get more food because he/she only has 3 days of food and the only way to get more food to last for the whole trip across the desert is to go back home several times and keep on storing food in the shelters. (Because the desert is "entirely lacking in resources")
-Mai I.

I agree with Madhula. I think it is 15 days.
-Sabrina H.

I still think my answer is correct…any counter?
its 15 days final?
if you disagree give a reason.

Less than 15 15 days more than 15
Brad Madhula Mark
Amir Mai name
David Sabrina name
name Sathvika name
name Henry name
name Rohan name
name name name

add your name where it belongs

i have no clue where Jonathan fits in here cuz he has just been writting stories…(add it for yourself Jonathan)

-Madhula A.

I know its 19 days but to lazy to give a reason we'll find out when he tells us the answer that im right
- Mark L

sorry i locked u mark..accident
And wow!!! how did you get 19 days???!!!
-Madhula A.

When Mark got 19 , he probably was really careful and took an extra day to rest before getting more supplies
◄ Henry C ◙

OMG!!i am cracking up…that is HILARIOUS!! *tear* *tear*
4 extra days of sleep is just too much mark…LOL!
But seriously Mark…how did you get 19 days?? I mean it could work, but we might want to use the shorter route. So if 15 days also works, then i would use the 15 day route…i son't think anyone wants to travel in a desert for 4 extra says…just saying. But plz explain how you got 19 days, there could be an error with 15 days that no one caught.
-Madhula A

mark- ur acting like me (rohan) for last problem.
madhulas explanation is the most accurate logical explanation ive heard
if ur right, ill be horribly surprised
prove that ur right


Everyone read this!!!!!!!!!!!!!!!!!!!!!
If you use a shelter you are using help which it says he doesn't and a desert lacking in resoures shouldn't have shelters in it. If anyone works at the shelters would die.
Brad S. out!

But why would that invalid the question if it was in there, in the first place… Unless your saying the problem can't be solved, but if that's true how come some many agree with Madhula's answer?
☼ Henry C æ

Exactly…it mentions that he has no help but he does have the shelters. The point of "no help" is to say that he doesn't have any "transportational" help. As in a random motorcycle that shows up near the 3rd shelter or something to help him get there faster….do u get what i mean??
-Madhula A

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