Quantitative Aptitude • Number System & SimplificationMedium
Three bells ring at intervals of 6, 10 and 18 seconds. If they ring together now, after how many seconds will they next ring together?
A. 90 seconds✓ Correct Answer
B. 1,080 seconds
C. 34 seconds
D. 180 seconds
💡 Solution & Explanation
The bells ring together again after a time that is a multiple of all three intervals, and the first such time is the LCM. LCM of 6 and 10 is 30, and LCM of 30 and 18 is 90. So the bells ring together again after 90 seconds. Adding the intervals or multiplying them gives a common time, but not the first one.