1. one number is 18 greater than another number . if the smaller number is subtracted from three times the
greater number , the result is 78. find the sum of the two numbers .
2. ABCD is a square . if AB=3x+3 and BC = 5x-11 , find the area of the square .
3. if a triangle has height (10-2x_ cm , base 9 cm and area (7-x)cm2 . find the vaLue of x .
吾該f.1 maths 吾識計(要過程)
2009-08-17 1:59 am
回答 (1)
2009-08-17 2:41 am
✔ 最佳答案
1)Let the small number be x , then the big number is x + 18 :
3(x + 18) - x = 78
2x = 78 - 18*3
x = 12
So the small number is 12 , the big number is 12+18 = 30
The sum of the 2 number = 12 + 30 = 42
2)
Since ABCD is a square , we have AB = BC ,
3x + 3 = 5x - 11
3 + 11 = 5x - 3x
14 = 2x
x = 7
AB = 3(7)+3 = 24 , the area of the square = 24*24 = 576
3)
height * base / 2 = area
(10 - 2x)*(9) / 2 = 7 - x
90 - 18x = 14 - 2x
90 - 14 = 16x
x = 4.75
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