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Cookie Jar

I need to know how to explain this problem.

There was a jar of cookies on the table. Amanda who was hungry, ate one seventh of the cookies. Then Beth came along and ate a third of what was left in the jar . Next Christine came by and decided to take a fifth of the remaining cookies with her to class.Then Danielle dashed up and took four cookies to eat. When Eleonor looked at the cookie jar, she saw that there were four cookies left. How man cookies were there in the jar to begin with?

Solution Preview

You have to work backwards. Here, at the end we have 4 cookies. We know that Danielle at 4 cookies so there were 8 cookies when she got there. Christine took a 1/5 of the cookies left which made 8 cookies left over. This means that 4/5 of the number of cookies that were there were left over (1/5 were taken and 4/5 were left). We know that 8 were left ...