# Help!

• July 1st 2006, 06:50 PM
laser2302
Help!

Find the speed in m/s of a point on a bicycle rim of diameter 88 cm, making 200 revolutions per minute.

and

Eight tins of paint are required for a surface of an area 50 m{square} if 4 coats of paint are applied. Find the number of tins of paint needed for an area of 70 m{square} if 5 coats of paint are applied.
• July 1st 2006, 09:04 PM
Quick
Quote:

Originally Posted by laser2302

Find the speed in m/s of a point on a bicycle rim of diameter 88 cm, making 200 revolutions per minute.

What you need to find first, is what is the circumference of the rim, which is $88\pi$

Now you need to find how many revolutions per second the rim goes, which is the amount rpm divide by 60 $200\div60=3\frac{1}{3}$

now we multiply the circumference by the rps and we get the answer...

$88\pi\times3\frac{1}{3}$ that gives us cm/s so we divide by 100 to get m/s

$\frac{88\pi\times3\frac{1}{3}}{100}$ and that is the answer in m/s (I don't have a calc. handy so you need to solve)
Quote:

Originally Posted by laser2302
and

Eight tins of paint are required for a surface of an area 50 m{square} if 4 coats of paint are applied. Find the number of tins of paint needed for an area of 70 m{square} if 5 coats of paint are applied.

If 8tins are required for 4 coats, than only 2 tins are required for 1 coat. If 2 tins are required to cover 50m^2, than 1 tin will cover 25m^2.

Now we need to figure out how many tins are required to cover 70m^2 with 1 coat. So we divide 70 by 25, $70m^2\div25m^2=2\frac{2}{5}$

so 2 and 2/5 tins are required for 1 coat, so now we multiply by 5 to get all 5 coats.

$2\frac{2}{5}\times5=12$ therefore, 12 tins are needed.