中二至中三數學題(3)

1. If a wheel rotates 60 times as it travels 30兀m,find its radius.
Its radius
= 30兀/(60兀*2)
= 1/4 m

2.A wire,32 cm long is bent into the shape of a quadrant.Find the area enclosed by the wire.
The area
= (32/4)^2
= 8^2
= 64 cm^2

3.A water pipe of internal diameter 2.6 cm delivers water at a rate of 0.8m/s.How much water comes out per second?
The amount of water comes out
= (2.6/2)^2 兀 * 0.8
= 4.25 cm^3 / s (corr to 3 sig fig)

中二至中三數學題(3)
1. If a wheel rotates 60 times as it travels 30兀m,find its radius.

30兀m = 60 x 2 x兀 x R
r =0.25 m


2.A wire,32 cm long is bent into the shape of a quadrant.Find the area enclosed by the wire.

32 = 2 x 半径 + 2 x兀 x R /4 （1/4圆周）
R = (32 x 2) / ( 4 + 兀) = 8.97 cm


3.A water pipe of internal diameter 2.6 cm delivers water at a rate of 0.8m/s.How much water comes out per second?

兀 x R2 (cmxcm)x 0.8 m/s = 3.14 x (2.6 / 10) x (2.6 / 10) x ( 0.8 x 10) = 1.7kg/s
厘米和米都专成分米（dm). 这样，得到的就是公斤，或千克水