Jonsey is awake for 2/3 of the day and spends 1/2 her time awake playing outside and the rest inside. Her brother, Riley, is awake for 3/4 of the day and spends 1/3 of his day outside and the rest inside. How much time, on average, do they spend inside? Let's think first. Chain of thought:
Jonsey is awake for 16 hours because 24 x (2 / 3) = 16. Jonsey spends 1 / 2 her day inside because 1 - (1 / 2) = 1 / 2. Jonsey spend 8 hours inside because 16 x (1 / 2) = 8. Riley is awake for 18 hours because 24 x (3 / 4) = 18. Riley spends 2 / 3 of his day inside because 1 - (1 / 3) = 2 / 3. Riley spends 12 hours inside because 18 x (2 / 3) = 12. In total they spend 20 hours inside because 8 + 12 = 20. On average, they spend 10 hours inside because 20 / 2 = 10.
Therefore, the answer is 10.