Mark plants some strawberries in his backyard. Every month, the number of strawberry plants doubles. After 3 months, Mark digs up 4 strawberry plants and gives them to his friend. If he still has 20 strawberry plants, how many did he initially plant?
Thoughts? Step-by-step reasoning:
First, add the 4 plants Mark gave away to the 20 he has left: 4 + 20 = 24. Then divide this number by 2 to find how many plants Mark had after two months: 24 / 2 = 12. Then divide that number by 2 to find how many plants Mark had after one month: 12 / 2 = 6. Finally, divide that number by 2 to find out how many plants Mark initially planted: 6 / 2 = 3.
Thus, the answer is 3.