use of formulae(3)幾題,好急！

2008-08-11 10:40 pm

1.A water tank,a m long,b m wide,c m deep,is full of water. What depth of water is left if x m既3次方 of water is pumped out?

2.A picture frame is a m long,b m wide. When a picture is mounted onto it, there is a border of uniform with c cm all round. Find the area of the picture in cm既2次方(面積)

3.A boy uses p% of his money in TV games and Q% of the remaining part in lunch. Whati is the percentage of his money being used?
要列式，唔該哂＞＜

更新1:

第3條打錯左.. 宜家改番: Whati is the percentage of his money being used? 變做 what is the percentage of his money being used?

回答 (1)

用戶10012

2008-08-11 11:44 pm

✔ 最佳答案

1.
Volume of water in the tank = abc.
Water pumped out = x^3
Therefore, water remaining = abc - x^3.
Since area of the tank = ab, therefore, new depth = (abc- x^3)/ab or c - x^3/ab.
2.
Width of picture = b - 2c.
Length of picture = a - 2c.
Therefore, area of picture = (b-2c)(a-2c).
3.
Let the boy has M money.
So money for TV game = M( 0.01p)
Money remaining = M - M(0.01p) = M( 1 - 0.01p).
Money for lunch = M(1-0.01p)( 0.01Q)
So total money used = M(0.01p) + M(1-0.01p)( 0.01Q)
So percentage used = [M(0.01p) + M(1-0.01p)(0.01Q)]/M
= [0.01p + (1-0.01p)( 0.01Q)] x 100%.

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