If you’ve got a 7-minute hourglass and an 11-minute hourglass how can you bake your cake for exactly 15 minutes more?
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To bake a cake in 15 minutes, follow these four steps.
- Begin baking the cake and flip both hourglasses at the same time.
- When the 7-minute hourglass empties, flip it over to start it again.
- Four minutes after that when the 11-minute hourglass empties, flip the 7-minute hourglass once more.
- Let the 7-minute hourglass run out, which will take another 4 minutes and bring you to 15 minutes of baking time.