A jar contains a total of 400 coins of 5 cents and 10 cents that add up to Tk 30. Find the number of 10-cent coins.

Question: A jar contains a total of 400 coins of 5 cents and 10 cents that add up to Tk 30. Find the number of 10-cent coins.

Solution:
Let,
the number of 10-cent coins be = x
So, the number of 5-cent coins is = (400 - x)

ATQ,
10x + {5 × (400 - x)} = (30 × 100)
⇒ 10x + 2000 - 5x = 3000
⇒ 5x = 1000
∴ x = 200

Therefore, there are 200 coins of 10 cents.