有無人可以教我計呢幾條數? FORM 2

用戶177179

2007-07-19 4:52 am

1) The length of a side of a square is measured as 6cm, correct to the nearest cm.
a) find the maxium erroe of the area of the square.
b) let x cm be the actual length of one side of the square, find the possible range of x.

2) if a:b:c = 5:2:1 and b+c =15, find a.

回答 (1)

Gabriella Montez

2007-07-19 5:32 am

✔ 最佳答案

( 1 a ) Maximum error of the measurement: 1 cm / 2 = 0.5 cm

The upper limit of the area : ( 6.5 )( 6.5 ) = 42.25cm2

Difference between the measured area : 42.25 – (6)(6) = 6.25cm2

The lower limit of the area : ( 5.5 )( 5.5 ) = 30.25 cm2

Difference between the measured area : ( 6 )( 6 ) – 30.25 = 5.75cm2

Hence the maximum error of the area of the square is 6.25cm2.

b) 5.5 < x < 6.5

( 2 ) Let a = 5k, b = 2k, c = k where k is a constant

b + c = 15

2k + k = 15

3k = 15

k = 5

Hence a = 5 ( 5 ) = 25

參考: My Maths Knowledge

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