4010 Shares

Topic: **Mathematical thinking and problem solving****Question:**
This is one part of a problem found in an Operations Research book published by Pearson Education.
Amy, Jim, John and Kelly are standing on the east bank of a river and wish to cross to the west side using a canoe. The canoe can hold at most two people at a time. Amy being the most athletic, can row across the river in one minute. Jim, John and Kelly would take 2,5, and 10 minutes, respectively. If two people are in the canoe, the slower person dictates the crossing time. The objective is for all four people to be on the other side of the river in the shortest time possible.
What is the smallest time for moving all four people to the other side of the river ?
In that book the answer given is 17 minutes.
How do you think, you shall answer and Why ?

June 19, 2019 / By Damia

Because of some mathematical correlation between the combination of people in the canoe and the order in which they cross.

👍 164 | 👎 8

Did you like the answer? We found more questions related to the topic: **Mathematical thinking and problem solving**

not exactly sure how to put it in words, but, for example (2,4) (6,4) (2,8) (6,8) It needs to look like that

17 is what I thought at first, because Amy would be the one to stay in the boat to get it back to the other side, and help each person across individually- someone needs to stay in the boat to take it back to the other shore. So really, only one new person at a time, the three slowest: so 10+5+2=17 But don't you have to take into account the crossing back time? so 17 is the trips there, and if Amy has to return twice, you have to add two minutes (1 minute per trip), so the answer would be 19 minutes.

👍 60 | 👎 2

Spiritually everything could be possible. Religiously, Mathematically and Operationally many colours could be possible like Anjanam can have (Anjanamennathu Njanarinju Manjalu pole Velutthum irikkum) or like 1 + 1 can have also "Immini Balya Onnu" and the same One.

👍 53 | 👎 -4

The best I can come up with (after twenty seconds of thinking) is this: 10 and 1 go=10 1 goes back=11 1 and 5 go=16 1 goes back=17 1 and 2 go=19

👍 46 | 👎 -10

I think they should go get the other canoe, because one canoe is just wasting time. Rather that or make the fastest one swim instead

👍 39 | 👎 -16

The lowest I can get is 19. 10 minutes-- 1st trip 1 minute back (amy alone) 5 minutes-- 2nd trip 1 minute back (amy alone) 2 minutes 3rd trip ----- 19 Unless they are not counting Amy's two back trips... but then what's the point?

👍 32 | 👎 -22

huh? Who's Operation Research? What's that to do with R/S? I didn't read the whole question because it started to sound like a trick atheist question or something for me to qualify for graduate school which are the same thing.

👍 25 | 👎 -28

Seems to me there are a couple of factors missing. I don't have an exact answer, but consider also the following: - Does "no wind" imply no evaporation? Only condensation (from the rain)? The former is exothermic, the latter endothermic. Or is that simply not a factor? Across only 100' (d), maybe it isn't, or at least not to any great extent. Humid environments increase the sensation of heat, as we all know. Standing in the rain causes cold, quickly, as heat is drawn away when the water vaporizes on the skin. - Could you (should you) factor in heart rate to the above. Running is X times more-vigorous to the average person vs. walking, though reduces time (t). That will raise body temperature and have other physiological side-effects. Might, or might not, be enough to calculate. - If (t) is 40 seconds (walking) vs. about 28.5 (running) to cross (d), should be easy enough to calculate the amount of water accumulated on the person, front and back, if you can calculate a surface area on said-person.

If you have your own answer to the question mathematical thinking and problem solving, then you can write your own version, using the form below for an extended answer.