# math

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Disks of radius 4 cm are cut from a rectangular plastic sheet of length 84 cm and width 24 cm. How many complete disks can be cut out? Find
(a) the total area of the discs out
(b) the area of sheet wasted

I did it but the answers on the back of the book do not match

heres what i did

no. of complete discs = (84*24) / 16pi
= 40
(a) total area of disc cut = 40*16pi
(b) area of wasted sheet = (84*24)-(40*16pi)
= 2016 - 2010 = 6

• math -

Assuming the discs (of diameter 8cm) are laid out in a rectangular grid, only 8 discs lie along the length, and the sheet is 3 discs wide.

That makes 30 discs.

If you want to change the layout, you can probably fit more discs, but you will never get 40 of them.

• math -

sorry - the sheet is 10 discs long (not 8)

• math -

thanks

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