UPSC Civil Services 2011 Prelims General Studies Paper II

Let the no. of ₹ 1 coins = x
and the no. of ₹ 2 coins = y
According to the question:
x + y = 50 ... (1)
x.1 + 2. y = 75 ... (2)
on solving (1) and (2), we get
2y – y = 75 – 50
⇒ y = 25
put value of y in equation (1), we get
x = 50 – y
= 50 – 25 = 25
Hence, number of ₹ 1 and ₹ 2 coins are 25 and 25 respectively.