Question

a cylindrical block is formed by placing coins of same size one above the other .the volume of block is 49.28 cm cube . if the radius of each coin is 1.4cm and thickness 0.2, then find the no. of coins arranged in block.plsanswer exam tomorrow

Answer 1

volume of one coin = πr²h
                                 = 3.14 ×1.4 ×1.4× 0.2
                                 = 1.232cm³
no.of coins = 49.28/1.232 = 40

Answer 2

For the coins:
radius, r = 1.4 cm
thickness, h = 0.2 cm

So, for the cylindrical block,
radius, r = 1.4 cm
height, H

Volume of cylinder = 49.28 cm³
∴π r² H = 49.28
∴22/7 * 1.4² * H = 49.28
∴22/7 * 1.96 * H = 4928 /100
∴H = (4928 * 7 * 100) / (100 * 22 * 196)
∴H = 34496 / 4312
∴H = 8 cm

Now, Height of cylinder is 8 cm.
So, number of coins = Height of cylinder / Height of 1 coin
                                 = 8 / 0.2
                                 = 40 coins
Thus, there are 40 coins in the cylindrical block.