Engineer's Puzzle

The Puzzle: Blowing a fuse

Blowers, a demolition engineer, has just set up two rounds of explosives around two old mill towers. He needs to detonate the explosives exactly 45 minutes apart to bring them down as he wants. But, he soon realises he left his watch at home. He thinks… ???

There are some old flares in the van he just brought. ‘These could be of use…’ he thought. The flares burn for exactly one hour after they’re lit. But, the flares don’t burn at a constant rate. One end burns away in 10 minutes while the other end takes 50 minutes.
Blowers, knows what to do. He grabs his lighter…

The question is, how can he measure 45 minutes?


Justin Cunningham

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