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# Help with a similar shapes question! Watch

1. A towel has a volume of 6100 cm3
The towel shrinks in a tumble drier. It remains a similar shape but its surface area decreases by 12%.
Find the new volume of the towel (to 3 sig. figs.)

- I don't know how to work out the original surface area in order to work out the scale factor, so that I can then work out the new volume... (If this is the correct logic behind working out this question)

Thank you
2. (Original post by RosaA)
A towel has a volume of 6100 cm3
The towel shrinks in a tumble drier. It remains a similar shape but its surface area decreases by 12%.
Find the new volume of the towel (to 3 sig. figs.)

- I don't know how to work out the original surface area in order to work out the scale factor, so that I can then work out the new volume... (If this is the correct logic behind working out this question)

Thank you
You don't need to. If the linear scale factor is then the area scale factor is and the volume scale factor is .

Here you have , so what's the volume scale factor?
3. (Original post by Zacken)
You don't need to. If the linear scale factor is then the area scale factor is and the volume scale factor is .

Here you have , so what's the volume scale factor?
So, if
s^2 = 0.88
s = 0.938083152

Volume = s^3
s^3 = 0.938083152^3
=0.8255131737

6100 cm^3 x 0.8255131737 = 5035.63036 cm^3
= 5035.63 cm^3 (3 sig. figs.)

4. (Original post by RosaA)
So, if
s^2 = 0.88
s = 0.938083152

Volume = s^3
s^3 = 0.938083152^3
=0.8255131737

6100 cm^3 x 0.8255131737 = 5035.63036 cm^3
= 5035.63 cm^3 (3 sig. figs.)

looks right
5. (Original post by Zacken)
looks right
I just realised, I made a mistake when changing the answer to 3 sig. figs. -sorry
It should be 5036 cm3

Thank you for the help!
6. (Original post by RosaA)
I just realised, I made a mistake when changing the answer to 3 sig. figs. -sorry
It should be 5036 cm3

Thank you for the help!
no problem!

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