Five Bells Begin to Toll Together and Toll Respectively at Intervals GMAT Problem Solving

Question: Five bells begin to toll together and toll respectively at intervals of 6, 7, 8, 9 and 12 seconds. How many times they will toll together in one hour?

  1. 5
  2. 6
  3. 7
  4. 9
  5. 14


Correct Answer: C

Solution and Explanation
Approach Solution 1:
This question has only 1 approach to model answer

The given condition of the problem states that five bells begin to toll together and toll respectively at intervals of 6, 7, 8, 9 and 12 seconds. Accordingly, it is to find the number of times all the five bells would toll together in 1 hour.

The intervals in which the five bells toll together respectively are at 6, 7, 8, 9, 12 seconds of interval.
Further, to get the number of seconds in regular intervals respectively, the five bells toll can be found by the Lowest Common Multiple of each second.

This equals to- 2^3 x 3^2 x 7 which equals to 504 seconds.

Significantly, the 1 hour has 3600 seconds so the number of times all the five bells would toll can be evaluated as follows:

3600/504 which equals to 7 along with a remainder.

Hence, the number of times the bells would toll together in an hour equals 7 times which is the correct answer that is option C.

“Five bells begin to toll together and toll respectively at intervals”- is a topic of the GMAT Quantitative reasoning section of GMAT. To solve GMAT Problem Solving questions a student must have knowledge about a good amount of qualitative skills. GMAT Quant practice papers improve the mathematical knowledge of the candidates as it represents multiple sorts of quantitative problems.


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