You have 2 unmarked buckets.

One holds 4 litres the other holds 7 litres.

You need to measure exactly 5 litres. You cannot estimate how much is in a bucket.

Scroll down for the solution

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Step 1) Fill the 4L bucket and empty it into the 7L bucket

Step 2) Fill the 4L bucket and pour 3L from it into the 7L bucket (now full) leaving 1L in the 4L bucket.

Step 3) Empty the 7L bucket

Step 4) Pour the remaining 1L from the 4L bucket into the 7L bucket

Step 5) Fill the 4L bucket and empty it into the 7L bucket which now contains 5L