Math CentralQuandaries & Queries


Question from Janice, a parent:

Wesley needs to move 820 kg of grain across the river in a canoe that can carry no more than 120 kg. Wesley has a mass of 70 kg. What is the fewest number of trips he will have to make? A. 17 trips; B. 18 trips; C. 32 trips; D. 33 trips.

Hi Janice,

Wesley has a mass of 70 kg and his canoe can hold a maximum of 120 kg so he can only put 120 - 70 = 50 kg of grain in the canoe with him. My question is "What is a trip?" By the wording and possible answers I think a trip is a one-way crossing of the river.

Does this help?

Janice wrote back


Your response did not help. I assumed that a trip was one way as well. This was on a homework worksheet. I emailed the teacher for help. Thank you for your help. We selected 17 as the answer, because the cargo can be no more 50kg which is the 120 -70. Dividing 820 by 50 is 16.4; so have less the least amount of trips would be the answer 17.

Thanks for your help.


I think 17 is a possible answer but 33 is also. Wesley has to cross the river 17 times with grain but he has to return to get more grain 16 times for a total of 17 + 16 = 33 trips.


About Math Central


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.
Quandaries & Queries page Home page University of Regina PIMS