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80/95 = .842105263
that's the empirical probability that the iris bulbs will bloom.
based on this probability, if she would like at least 91 to bloom, she should plant at least 91/.842105263 = 108.90625 bulbs.
this should be rounded up to 91.
she plants 91 and .842105263 * 91 of them bloom.
this would come out to be 91.78947365 bulb will bloom, which rounds down to 91.