Sally is making sun tea. Every hour, the concentration of the tea doubles. If it takes 6 hours for the tea to be ready, how long would it take for the tea to reach half of the final concentration (in hours) ?

It will be at half the concentration at hour 5.

If it double every hour, this means it would have to be at half the concentration the hour before the 6th hour in order to double to get the full concentration in the sixth hour.

X2 x 2 x 2 x 2 x 2 x 2

2, 4, 8, 16, 32, 64

32 is half of 64.