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Difficult donkey

David Shaw

5 February, 2020

Difficulty: Taxing

Darryl wants to ride his donkey from Alphaville to Betatown.

The donkey is always hungry and will only walk if Daryl keeps feeding her apples. She will eat one apple per kilometre they travel.

Darryl’s donkey can carry Darryl, Darryl’s luggage and 60 apples. Unfortunately, it’s 80 kilometres from Alphaville to Betatown.

Daryl has plenty of money to buy apples in Alphaville – he can buy hundreds if he needs them. But there’s nowhere to buy them between Alphaville and Betatown. Is there any way for him to complete his journey?

Scroll down or click for a hint, or the answer!

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Brainteaser hint

Darryl can hide some apples along the way!

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Brainteaser answer

It’s possible but it’ll take a few trips.

Darryl needs 20 more apples than the donkey can carry. If Darryl stashes 20 apples somewhere on the path, he can load up midway and keep going.

One solution is:

Load up with 60 apples at Alphaville, then ride 20 kilometres towards Betatown. Darryl now has 40 apples left. Hide 20 apples and then ride home to Alphaville.

Load up again with 60 apples, ride 20 kilometres and find the hidden apples. Darryl has 40 apples, and collects 20 more, making 60 in total. It’s now 60 kilometres to Betatown, so Darryl can ride straight there!

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Categories:

Brainteaser, Maths

Tags:

donkey, mathematical sciences, number, problem solving

5 responses

Hollie

7 February, 2020

Maybe Darryl should just walk the first 20km and carry 20 apples, he’d probably get there quicker and he’d get his 10,000 steps for the day :p
Don’t be lazy Darryl

Reply
Trish

7 February, 2020

Totally agree with Hollie, that was my thinking.

Reply
Ayumiao

7 February, 2020

Or just take 20 apples in the luggage, leaving some of his own stuff behind! What if some other donkey comes and eats the stashed apples?

Reply
Tim

9 February, 2020

If Darryl walks, he’ll probably need to eat the apples too. Travel light – or since he has so much money, he can just buy new luggage when he arrives. Might even be a good op shop in Betatown.

Reply
Terry

10 February, 2020

“Daryl wants to RIDE his donkey from A to B”. The solutions have riding the donkey from A to 1/3 B and back to A then A to B. Or Daryl walking A to 1/3 B, not riding all the way A to B.
If Daryl rides from A to 2/3 B and secures his donkey to a tree, walks to B to get apples and walks back to 2/3 B and rides his donkey to B he accomplishes his stated goal of riding from A to B. Riding a donkey 80 km you probably stop to eat, drink, stretch or use a bathroom. So getting off the donkey would not violate the spirit of his goal. And the first solution would, at minimum, include getting off the donkey to retrieve the apples which you could not leave out without expecting them to be taken. I feel this solution stays within the spirit of Daryl’s goal of riding A to B.

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