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0 / 60 seg.
The world's tallest skyscraper took seven years to build. Each year the workmen were able to double its height. How many years did it take for the skyscraper to reach half of its maximum height?
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Clue
HE IS 16 YEARS OLD. WHEN I WAS 4 YEARS OLD, MY BROTHER WAS 2 YEARS OLD (HALF MY AGE), SO MY BROTHER IS 2 YEARS YOUNGER THAN ME. WHEN I AM 18 YEARS OLD, MY BROTHER WILL BE 16 YEARS OLD AS HE IS 2 YEARS YOUNGER THAN ME
180 CENTIMETRES. HALF OF HIS HEIGHT IS 90 CENTIMETRES. THEREFORE HIS FULL HEIGHT HAS TO BE DOUBLE OF THAT
THE NAIL WOULD BE AT THE SAME HEIGHT AS TREES GROW FROM THE TOP
SIX YEARS. THE WORKMEN WERE ABLE TO DOUBLE ITS HEIGHT EVERY YEAR, SO IT SHOULD BE HALF OF ITS MAXIMUM HEIGHT ONE YEAR BEFORE COMPLETION
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