if there are 70 grains of sand in 3 tablespoons, how many grains of sand are in 2 tablespoons?

46.67 grains of sand in 2 tablespoons.

For this sort of question, you can find out how many are in one and then multiply by the new number of tablespoons:

70/3 = 23.3

23.3 x 2 = 46.6

70 x 2/3 = 140/3 = 46.666.... Say 47.

Using the unitary method, we find that (if there are 70 grains of sand in 3 tablespoons) in one tablespoon there is 70/3 grains of sand. This said, in 2 tablespoons we would have 2 * 70/3. This is 46.666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666.................

so it is around 46/47 grains of sand...

(That is a very silly question to ask a student though)

About 47

About 46.

2/3 x 70 = 140/3 = 46 full grains

70 : 3 = x : 2

70/3 = x/2

3x = 70 x 2

x = 140/3

= 46 2/3

47 grains of sand

The answer can be 2 or 69, or a number between these two!

Edit: how you know that there are a same amount of grains in the spoons?