Ek riddle..
You have 9 identical coins..
8 coins are of same weight, but one coin is ligher from others..
You have one ⚖️, for weighing. But you can use it only twice..
How can you find lighter coin from all 9 coins♂️
Answers
Answer:
Take a random coin and keep it aside
Now divide the coins in equal and weigh them if they weigh equal then the random coin choosen is lighter than the other 9 coins
Hope you understand
thankyou
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Solution :-
Let us assume that, 9 identical coins are denoted as 1, 2, 3, 4, 5, 6, 7, 8 and x . where x is lighter in weight from others .
Divide 9 coins into pair of 3 . Say (1, 2, 3) , (4, 5, 6) and (7, 8, x) .
Case 1) :- Taking any two pairs and weighing them .
- (1, 2, 3) and (4, 5 ,6) = They are equal . The lighter coin is in third pair .
- (1, 2, 3) and (7, 8, x) = They are not equal . The coin is in heavier pair .
- (4, 5, 6) and (7, 8, x) = They are not equal . The coin is in heavier pair .
from this we can conclude that, x is in (7, 8 , x) .
Case 2) :- Taking any two coins and weighing them .
- if we take 7 and 8 they will be equal and we get left coin x as lighter .
- if we take 7 and x , 7 will be heavier and we gets x .
- if we take 8 and x , 8 will be heavier and we gets x .
Hence, only in two case we can find which coin is lighter .
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