India changed over from the old non decimal rupee anna system to the modern decimal system of coinage in which year and month?

Introduction / Context:
Before decimalisation, India used a complex system of coinage based on rupees, annas and pies, where one rupee equalled sixteen annas and one anna equalled twelve pies. For simplification and to align with international practice, India later switched to a decimal system where one rupee equals one hundred paise. This change is an important event in the country s monetary history and often appears in general knowledge questions. The key fact to remember is the specific year and month when decimal coinage was officially introduced.

Given Data / Assumptions:

• The event is the change to the decimal system of coinage.
• We are asked for the year and month only, not for the exact date.
• Options give various April dates in different years around independence and later.
• We must match the correct year of decimalisation.

Concept / Approach:
The Indian Coinage (Amendment) Act paved the way for decimalisation, and the new system came into force on 1 April 1957. On that date, the rupee was divided into one hundred units called paise, initially known as naya paise to differentiate them from the older units. Knowing this date allows you to select the correct year and month whenever the question appears in simplified form. Since the question only requires the month and year, we focus on April 1957 rather than remembering the exact day as well.

Step-by-Step Solution:
Step 1: Recall that India did not immediately adopt a decimal system after independence in 1947; the old rupee anna system continued for some years. Step 2: Remember that the major monetary reform to decimalise the rupee came into effect on 1 April 1957. Step 3: Note that option B states April 1957, which matches this year and month exactly. Step 4: Check that no other option lists 1957 and that all other years are either earlier or slightly later than the correct one. Step 5: Choose April 1957 as the correct answer.

Verification / Alternative check:
Standard references on the history of Indian currency and RBI publications confirm that decimal coinage started in India from 1 April 1957. Textbooks and competitive exam guides consistently mention this date as the point when naya paisa was introduced and the old anna system began to be phased out. Since the question only needs the month and year, April 1957 is the verified answer.

Why Other Options Are Wrong:
April 1947: This is before Indian independence and far too early for such a major monetary reform. April 1956: This is one year earlier than the actual introduction of decimal coinage. April 1949: Although monetary policies evolved after independence, full decimalisation did not occur in this year. April 1961: This is later than the actual date; by 1961, decimal coinage had already been in operation for a few years.

Common Pitfalls:
Candidates often confuse the introduction of decimal coinage with other economic events such as bank nationalisation or currency changes. Another pitfall is to assume that such a reform must have happened either immediately after independence or much later, without remembering the specific mid point of 1957. To avoid this, it is useful to memorise the small set of key economic dates, including 1 April 1957 for decimalisation, as this fact is repeatedly tested in general awareness sections.

Final Answer:
India changed over to the decimal system of coinage in April 1957.