A cashier has 30 coins made up of ₱5 and ₱10 coins, worth ₱210 in all. How many ₱5 coins are there?
Correct answer: C. 18
If all 30 coins were ₱10 coins they would be worth ₱300, which is ₱90 too much. Each ₱5 coin reduces the total by ₱5, so there are 90 ÷ 5 = 18 five-peso coins and 12 ten-peso coins. Check: 90 + 120 = 210.
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