A bookstore had 70 copies of a magazine. Yesterday, it sold 1/5 of them. Today, it sold of what remained. How many copies does the bookstore have left?
To find out how many copies the bookstore has left, we need to calculate the number of copies sold on both yesterday and today, and then subtract it from the initial number of copies.
Let's start by finding out how many copies were sold yesterday. We are told that 1/5 of the total copies were sold, so we need to calculate 1/5 of 70.
1/5 x 70 = 14
Therefore, 14 copies were sold yesterday.
Now, let's calculate how many copies were sold today. We are told that today's sales were 3/10 of what remained. So, we need to calculate 3/10 of (70 - 14), which is the number of copies remaining after yesterday's sales.
(70 - 14) = 56
3/10 x 56 = 16.8
Since we cannot have a fraction of a magazine, we can assume that 16 magazines were sold today.
Now let's subtract the total number of copies sold (yesterday + today) from the initial number of copies to find out how many are left.
Initial number of copies = 70
Copies sold = 14 + 16 = 30
70 - 30 = 40
Therefore, the bookstore has 40 copies of the magazine left.