It is given Sally is making sun tea. Every hour the concentration of the tea doubles.Let the concentration of tea at start is nil.Then after first hour concentration will be 2.After third hour concentration will be double of 2 that is 4.After fourth concentration will be 4(2)=8.After fifth hour concentration will be 8(2)=16.After sixth hour concentration will be 16(2)=32.
It is given:it takes 6 hours for the tea to be ready.WE need to find how long would it take the tea to reach half of the final concentration.Half of final concentration is 32÷2=16.
Concentration of 16 is after fifth hour.