Question

I have 25 coins in my pocket all of which are 5 penny or 20 penny coins. if their total value is 2.90 pounds how many penny coins do I have?

Answer 1

• 14 coins of 5p
• 11 coins of 20p

Explanation:

Given

• 5p coins = x
• 20p coins = y
• Total = 2.90 = 290 p
• Number of coins = 25

Equations

• x + y = 25
• 5x + 20y = 290 ⇒ x + 4y = 58

Consider the first equation in the second one

• x + y + 3y = 58
• 25 + 3y = 58
• 3y = 33
• y = 11

Then x is

• x = 25 - 11 = 14

Answer

• 14 off 5p coins and 11 off 20p coins