Question

What will be the minimum number of weighings required to find the packet with defected chocolates if the defected chocolates weigh either 9 or 11 grams each (all defected chocolates will have the same weight)?

• A. 1
• B. 2
• C. 3
• D. More than 3

Answer 1

The correct option is A 1

We know that one of the packets contains chocolates with 9 grams weight each. Let us take 1 chocolate from 1st packet, 2 chocolates from 2nd packet, 3 chocolates from 3rd packet and so on till 10 chocolates from 10th packet. In total we have 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 55 chocolates. Ideally the weight should have been 55 $\times$ 10 = 550 grams.
Let us say the electronic balance shows the weight as 555 grams, we can say 5 chocolates are defected and hence 5th packet is the one with defected chocolates (weighing 11 grams). If the weight is 546 grams, we can say 4 chocolates are defected and defected chocolates with 9 grams. Hence, let us say the nth packet is defected, n = (Weight being shown by the balance - 550). So, only I weighing is sufficient.