We are given : The mass of a grain of sand =
Bag contains = 10 kilograms of sand.
Let us concert 10 kg into grams first.
1 kg = 1000 grams.
10 kg = 10 × 1000 = 10000 grams = 10^4.
Therefore, bag contains 10^4 grams of sand.
Therefore, number of grains of sand are in the bag of sand of 10^4 grams =
The mass of a grain of sand in grams ÷ The mass of a grain of sand.
=
=
Therefore, grains of sand are in the bag of 10kg sand.