 Hello and welcome to the session I am Deepika here. Let's discuss a question which says how many silver coins 1.75 cm in diameter and of thickness 2 mm must be melted to form a cuboid of dimensions 5.5 cm by 10 cm by 3.5 cm. Now in this question we have to find the number of silver coins which must be melted to form a cuboid of given dimension. First recall the formula for volume of a cylinder. Volume of a cylinder is equal to square H where R is the radius of the base of the cylinder and H is the height of the cylinder and volume of a cuboid equal to length that is L into breadth B into height H. So this is the key idea behind our question. We will take the help of this key idea to solve the above question. So let's start the solution. Now we have given the diameter of the coin is equal to 1.75 cm therefore radius of the coin is equal to 1.75 upon 2 cm. Now it is also given the thickness of a coin is 2 mm and this is equal to upon 10 cm because 1 cm is equal to 10 mm and 1 mm is equal to 1 by 10 cm therefore 2 mm is equal to 2 by 10 cm and this is again equal to 0.2 cm. Now first we will find the volume of one coin. So volume of one coin is equal to R square H and this is equal to take pi is 22 upon 7 into R is 1.75 upon 2 cm which is the thickness of a coin. This is 0.2 cm so volume of one coin is 22 upon 7 into 1.75 upon 2 into 1.75 upon 2 into 0.2 cm cube. So we have volume of one coin is equal to now on cancellation we have this is equal to 11 into 0.25 into 1.75 into 0.1 cm cube. Now volume of cuboid is equal to B into H. Now length is 5.5 cm, breadth is 10 cm and height is 3.5 cm. Therefore volume of a cuboid is 5.5 into 10 into 3.5 cm cube. Now we want to find the number of coins which must be melted to form a cuboid of dimensions 5.5 cm by 10 cm by 3.5 cm. So number of coins is equal to volume of a cuboid upon volume of one coin. Now volume of a cuboid is 5.5 into 10 into 3.5 cm cube upon volume of one coin is 11 into 0.25 into 1.75 into 0.1 cm cube. Now we will solve this. So first let us remove the decimal point from the decimal numbers. So this is equal to 55 into 10 into 35 into 100 into 100 into 10 upon 11 into 25 into 175 into 1 into 10 into 10 because 5.5 is equal to 55 upon 10 and 3.5 is equal to 35 upon 10. Similarly 0.25 is 25 upon 100 and 1.75 is 175 upon 100 and 0.1 is 1 upon 10. So on cancellation we have so this is equal to 10 into 4 into 10 and this is equal to 410. The number of coins which must be melted to form a cuboid of given dimensions is equal to 400. Hence the answer for the above question is 400. I hope the solution is clear to you. Bye and take care.