f.1 easy math

咩問題嚟架,串法同Grammar都錯哂!我估兩條問題可能應該係咁:
1. The difference between two numbers is 15. The sum of the larger number and 8/5 of the smaller number is 54. Find the larger number.
F.1應該唔使計2元1次方程掛...
咁我用1元1次方程嘅方法啦

Let x be the required larger number.
then the smaller number = x-15
∴(8/5)x+(x-15) = 54
(13/5)x-15 = 54
(13/5)x = 39
x = 15
∴The larger number is 15.

2. There are some chickens and rabbits in a cage. 1/3 of the rabbits have 3 legs. If the total number of heads is 35 and the total number of legs is 90, find the number of
(a) chickens
(b) rabbits with 4 legs

Let n be the number of chickens.
Number of animals = Number of heads = 35
Number of rabbits = 35-n
Number of rabbits with 3 legs = (1/3)(35-n)
Number of rabbits with 4 legs = (2/3)(35-n)
Total number of legs = 2n+3[(1/3)(35-n)]+4[(2/3)(35-n)] = (5/3)(77-n)
∴(5/3)(77-n) = 90
77-n = 54
n = 23
(a) The number of chickens is 23.
(b) The number of rabbits with 4 legs = (2/3)(35-n) = (2/3)(35-23) = 8

2007-12-21 21:33:04 補充：
第1題我計錯咗:Let x be the required larger number.then the smaller number = x-15∴x (8/5)(x-15) = 54(13/5)x-24 = 54(13/5)x = 78x = 30∴The larger number is 30.