A milkman wants to empty a large drum filled with milk using one of the four measuring jars with capacities of 6, 9, 15, and 18 liters respectively. He finds that regardless of which jar he uses, there are always 4 liters of milk left in the drum. If the capacity of the drum is a multiple of 7, what is its minimum possible capacity?

Correct option is B

Given:
Drum leaves 4 liters after using any jar (6, 9, 15, 18 liters).
Drum capacity is a multiple of 7.
Find the minimum possible capacity.
Solution:
LCM of 6, 9, 15 and 18 is 90
According to the question
Volume of drum = (90n + 4) liters
Where, n is any natural number and (90n + 4) is divisible by 7
When
n = 1, 90n + 4 = 94, which is not divisible by 7
n = 2, 90n + 4 = 184, which is not divisible by 7
n = 3, 90n + 4 = 274, which is not divisible by 7
n = 4, 90n + 4 = 364, which is divisible by 7
∴ The least possible volume of the drum is 364 liters.
Alternate Solution:
​As per the given condition, the least possible volume must be a multiple of 7.
​Among the given options, 364 is the only number that is divisible by 7.
∴ The minimum possible volume of the drum is 364 liters.​