You are given 6 identical balls of same size and shape two of which are red. two white and two blue. It is known that one ball of each colour weighs 15 gm; while the other weighs 16 gm. Using a two-pan balance only twice how will you separate the balls of 16 gm weight?
Call the balls R1, R2, W1, W2, B1, B2.
First weighing: R1 & W1 vs B1 & W2
If: R1+W1 = B1+W2
Weigh: R1 vs B1
R1 < B1 R1 = B1 R1 > B1
------- -------- -------
W1>W2 impossible W1<W2
R1<R2 R1>R2
B1>B2 B1<B2
If: R1+W1 < B1+W2
Weigh R1 vs B2
R1 < B2 R1 = B2 R1 > B2
------- -------- -------
W1<W2 W1<W2 W1<W2
R1<R2 R1<R2 R1>R2
B1<B2 B1>B2 B1>B2
If: R1+W1 > B1+W2
Weigh R1 vs B2
R1 < B2 R1 = B2 R1 > B2
------- -------- -------
W1>W2 W1>W2 W1>W2
R1<R2 R1>R2 R1>R2
B1<B2 B1>B2 B1<B2
|
|
Posted by Charlie
on 2013-01-09 18:11:00 |
solution
