self Maths Puzzle

One of twelve pool balls is a bit lighter or heavier (you do not know) than the others.

At least how many times do you have to use an old balance-type pair of scales to identify this ball?

Read Solution (Total 2)

self Other Question

Real jelly babies have a mass of 10 grams, while imitation jelly babies have a mass of 9 grams.

Spike has 7 cartons of jelly babies, 4 of which contain real jelly babies, the others imitation.

Using a scale only once (and minimum disturbace of the boxes contents!), how can Spike determine which cartons contain real jelly babies?
Solve this:

ALFA + BETA + GAMA = DELTA