Question

There are 3 red marbles for every 7 blue marbles in a box.

If the box has 40 marbles, how many marbles are blue?



______ marbles are blue.

Answer 1

That means that for every ten marbles, 7 are blue.

40 = 4 * 10

4 * 7 = ?

Answer 2

3 red marbles + 7 blue marbles = 10 marbles

The box has 40 marbles , that is 4 times more than 10.

4 ∙ 7 = 28 blue marbles

4 ∙ 3 = 12 red marbles

Checking the results:

7 blue marbles / 3 red marbles = 28 blue marbles /12 red marbles

7 / 3 = 28 / 12

7 / 3 = 4 ∙ 7 / 4 ∙ 3 = 7 / 3