Solution

To find the day of the week on 25th April 1960, we calculate the number of odd days from the reference date (1st January 1900) to 25th April 1960.

 

Number of years from 1900 to 1959: 60 years

Ordinary years: 45

Leap years: 15

 

Total number of odd days:

Odd days from 45 ordinary years: \(45 \times 1 = 45\)

Odd days from 15 leap years: \(15 \times 2 = 30\)

Total odd days = 45 + 30 = 75

 

Reducing the total odd days modulo 7:

75 ÷ 7 gives a remainder of 5, so there are 5 odd days.

 

Odd days from 1st January 1960 to 25th April 1960:

January: 31 days = 3 odd days

February (1960 is a leap year): 29 days = 1 odd day

March: 31 days = 3 odd days

April: 25 days = 4 odd days

Total odd days from 1960 = 3 + 1 + 3 + 4 = 11 odd days = 4 odd days (mod 7)

 

Final calculation:

Total odd days = 5 + 4 = 9 odd days

Reduced modulo 7:
9 mod  7 = 2 odd days

 

Day corresponding to 2 odd days = Monday