is throwing a fancy dinner party,

他們打算要辦場很炫的晚餐派對，

and they all want to look their best.

他們都希望能展現 自己最好的樣子。

But there's a problem –

但有一個問題——

the elder giant's favorite shirt is wrinkled!

年長巨人最愛的襯衫是皺的！

To fix it, you'll need to power up…

為了解決這個問題，你需要啟動

the Giant Iron.

巨型熨斗。

The iron needs two giant batteries to work.

熨斗需要兩個巨型電池才能運作。

You just had 4 working ones

你有四個電池是能用的，

and 4 dead ones in separate piles,

四個已經沒電的， 分別放在不同堆，

but it looks like the baby giant mixed them all up.

但看來巨人寶寶 把它們都混在一起了。

You need to get the iron working and press the giant shirt, fast –

你得要盡快讓熨斗能運作 並把巨人的襯衫燙平——

or you'll end up being the main course tonight!

不然你可能就要 變成今晚的主菜了！

How can you test the batteries

你要如何測試電池，

so that you're guaranteed to get a working pair in 7 tries or less?

才能確保不超過七次嘗試

Pause the video now if you want to figure it out for yourself

就找出一對可以用的電池？

Answer in 3

如果你想要自己試著解題， 請在這裡暫停。

Answer in 2

答案即將公佈：三

Answer in 1

答案即將公佈：二

You could, of course, take all eight batteries

答案即將公佈：一

and begin testing the 28 possible combinations.

當然，你可以把所有電池拿來，

You might get lucky within the first few tries.

測試所有二十八種可能的組合。

But if you don't, moving the giant batteries that many times

你可能會走運， 在前幾次嘗試就成功。

will take way too long.

但如果沒成功，把巨型電池 搬來搬去那麼多次，

You can't rely on luck –

會花太長的時間。

you need to assume the worst possibility and plan accordingly.

你不能仰賴運氣——

However, you don't actually need to test every possible combination.

你得要假設最糟糕的可能狀況， 並依此來做計畫。

Remember – there are four good batteries in total,

然而，你並不需要真的測試 每一種可能的組合。

meaning that any pile of six you choose

別忘了——總共有 四個可以用的電池，

will have at least two good batteries in it.

意思就是，你只要 任意選六個電池，

That doesn't help you right away,

裡面一定至少有兩個可以用的。

since testing all six batteries could still take as many as 15 tries.

那並不能馬上解決問題，

But it does give you a clue to the solution –

因為測試所有六個電池 最多也可能要做十五次嘗試。

dividing the batteries into smaller subsets narrows down the possible results.

但至少這讓你對於 解決方案能有點頭緒——

So instead of six batteries,

將電池分開成比較少的子集合， 來把可能的結果減少。

let's take any three.

所以，不要選取六個電池，

This group has a total of three possible combinations.

咱們任選三個就好。

Since both batteries have to be working for the iron to power up,

這一組總共有三個可能的組合。

a single failure can't tell you whether both batteries are dead, or just one.

因為如果要啟動熨斗， 兩個電池都得要是有電的，

But if all three combinations fail,

熨斗沒啟動，無法讓你確定

then you'll know this group has either one good battery, or none at all.

是兩個電池都沒電， 還是只有一個沒電。

Now you can set those three aside

但如果三個組合都沒能啟動熨斗，

and repeat the process for another three batteries.

你就知道這組當中可能 有一個電池有電，或通通都沒電。

You might get a match, but if every combination fails again,

現在，你可以把 這三個電池放一邊，

you'll know this set can have no more than one good battery.

再對另外三個電池重覆這個流程。

That would leave only two batteries untried.

你可能可以讓熨斗啟動， 但如果每種組合又都失敗了，

Since there are four good batteries in total

你就知道這一組裡面 有電的電池最多只有一個。

and you've only accounted for two so far,

就只剩下兩個電池還沒試過。

both of these remaining ones must be good.

既然總共只有四個有電的電池，

Dividing the batteries into sets of 3, 3, and 2

你目前也只算出有兩個有電的，

is guaranteed to get a working result in 7 tries or less,

最後剩下的這兩個 就一定都是有電的。

no matter what order you test the piles in.

將電池分組為三個、三個、兩個，

With no time to spare, the iron comes to life,

就能確保在七次嘗試之內 讓熨斗啟動，

and you manage to get the shirt flawlessly ironed.

不論你用什麼順序 來測試這些電池都可以。

The pleased elder and his family show up to the party dressed to the nines

沒有多餘時間可浪費， 熨斗起死回生了，

… well, almost.

你得以把襯衫燙平，完美無瑕。