self Maths Puzzle

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?

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self Other Question

You have eight bags, each of them containing 48 coins.

Five of these bags contain only true coins, the rest of them contain fake coins.

Fake coins weigh 1 gram less than the real coins. You do not know what bags have fake coins and what bags have real coins. You can use a scale with precision up to 1 gram. Making only one weighing and using the minimum number of coins, how can you find the bags containing the fake coins? 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?