Seven cubes are identical in shape. Out of these, the weight of each of the six cubes is equal and the weight of the remaining cube is less than the weight of any other cube. A balance is used to identify the lightest cube. What is the minimum number of attempts required to distinguish the odd cube with certainty?
- AOption (a)
2
- BOption (b)
3
- COption (c)
4
- DOption (d)
1
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Correct answer
2
Why this answer is correct
Given:
There are 7 cubes. 6 cubes have equal weight and 1 cube is lighter.
We need to find the lightest cube using a balance.
First Attempt:
Divide the 7 cubes into:
- 3 cubes on left side
- 3 cubes on right side
- 1 cube aside
Case 1: If both sides balance, then the remaining cube is the lightest.
Case 2: If one side is lighter, then the lightest cube is among those 3 cubes.
Second Attempt:
From the suspected 3 cubes, compare:
1 cube vs 1 cube
If one side is lighter, that cube is the answer. If both balance, then the third cube is the lightest.
Therefore, the minimum number of attempts required is 2.
Hence, the correct answer is "Option 1".