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Today Puzzle #644

Puzzle No. 644– Wednesday 1 January

Deforestation of Brazil's Amazon rainforest increased by 30% in 12 months, the highest rate since 2008, the country's space agency reports. This year ten thousand square kilometres were lost. If this increases by 30% every year how long will it take for the remaining 3.3 million square kilometres of the Amazon rainforest to disappear completely? (Hint, or rather warning, we are talking not many 10s of years.)

Today’s #PuzzleForToday has been set by Dr Shaun Fitzgerald, Director of the Royal Institution

Click here for the answer

Yr 1 We are looking for the number of terms in the series 10,000 x (1.3 + 1.3x1.3 + 1.3x1.3x1.3 …) which are required to first exceed 3,300,000. 17 terms in the series are required and hence the rainforest will be lost after 17 years.

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