Doris earns $20 per hour by babysitting. She needs to earn at least $1200 for her monthly expenses. She can babysit for 3 hours every weekday and 5 hours on a Saturday. How many weeks does it take for Doris to earn enough to cover her monthly expenses? Let's think first. Chain of thought:
Doris babysits for a total of 5 weekdays x 3 hours / weekday = 15 hours. She babysits for a total of 15 + 5 = 20 hours in a week. She earns 24 x $20 = $480 in a week. So, it will take $1440 / $480 = 3 weeks to earn Doris needed amount.
Therefore, the answer is 3.