108 identical books have a mass of 30kg.find the number of such books that has a mass of 20kg.
x/20 = 108/30
x = 20*108 ÷ 30 = ....
2/3 the mass, so 2/3 the books
2/3 * 108 = 72
To find the number of books that have a mass of 20kg, we need to use the concept of ratio and proportion.
First, let's determine the mass of a single book by dividing the total mass of 108 books by 108:
Mass of a single book = Total mass / Number of books
Mass of a single book = 30kg / 108
Mass of a single book ≈ 0.278kg
Now, we can set up a proportion to find the number of books that have a mass of 20kg. Let's call this unknown number of books "x":
0.278kg / 1 book = 20kg / x books
To solve for "x", we can cross-multiply:
0.278kg * x = 1 book * 20kg
0.278x = 20
x = 20 / 0.278
x ≈ 71.94
Therefore, approximately 72 books have a mass of 20kg.