Math Problem of the Week - Middle School - July 18, 2021 to July 24, 2021

Middle School: 

Question: Lisa needs to memorize the locations of all 54 countries in Africa for a geography test that will be 30 days from now. She memorizes 7 countries every 3 days. Every 2 days, she forgets a country and needs to re-memorize it. Will she have enough time to memorize all of the countries in Africa for her geography test? 

Answer: Yes

Solution: Since there are 10 3-day periods in 30 days, Lisa can memorize the location of a country a total of 7 × 10 = 70 times. That means she has time to forget and relearn 70 – 54 = 16 of them. If she forgets 1 every 2 days, that means she forgets 30 ÷ 2 = 15 of them, and since 15 is less than 16, she will have time to re-memorize them all.