Today's Daily Quiz is Live — Test your knowledge & improve your rank
|
Interview Brain Teasers Medium 3 min

An interviewer gives you 8 identical balls. One ball is slightly heavier than the others. Using a balance scale, what is the minimum number of weighings required to guarantee finding the heavier ball?

Hint
Divide the balls into groups as evenly as possible.

Answer

2 weighings.

Explanation

Divide the balls into groups of 3, 3 and 2. Weigh 3 against 3. If they balance, the heavier ball is among the remaining 2 and one more weighing identifies it. If they do not balance, the heavier ball is in the heavier group of 3 and one additional weighing identifies it.

Step-by-Step Solution

Weigh 1: 3 vs 3.
If balanced, weigh the remaining 2.
If unbalanced, weigh 1 vs 1 from the heavier group of 3.
6 puzzles
You have eight identical-looking balls, but one is heavier than the others. Using a balance scale, what is the minimum number of weighings needed to identify the heavier ball?
11 views Interview Brain Teasers
Medium
You have 9 identical-looking balls and one is heavier. What is the minimum number of balance-scale weighings needed to find it?
11 views Interview Brain Teasers
Hard
An interviewer gives you two ropes. Each rope takes exactly one hour to burn, but they do not burn at a uniform rate. How can you measure exactly 30 minutes?
13 views Interview Brain Teasers
Medium
You have a building with 100 floors and two identical glass balls. You need to determine the highest floor from which a ball can be dropped without breaking, while minimizing the worst-case number of drops. What is the classic strategy based on?
19 views Interview Brain Teasers
Hard
You have 8 identical-looking balls and one is heavier. What is the minimum number of balance-scale weighings needed to guarantee finding it?
11 views Interview Brain Teasers
Medium
Why are manhole covers usually round rather than square?
10 views Interview Brain Teasers
Medium