f1英文數學

第1題:
Let the 2-digit no. be 10a + b
Given the no. is divisible by both 2 and 5,
Because 2 * 5 = 10, the no. is a multiple of 10
Therefore, b = 0
Given ½ (10a + b) = 6a - 4
½ (10a + b) x 2 = (6a - 4) x 2
10a + b = 12a - 8
8 = 2a
4 = a
a = 4
10 a + b = 10 * 4 + 0 = 40

Ans. The 2-digit number is 40.

第2題+第3題:

Let x be the number of chickens and y be number of rabbits.

The total number of heads is 35
x + y = 35 --- (1)

1/3 of the rabbits were born to have 3 legs
Total number of legs is 90
2x + 3(1/3y) + 4(2/3y) = 90
2x + 11/3y = 90 --- (2)

By (2) - 2*(1):
5/3y = 20, y = 12, x = 23

So, Number of chickens: 23
Number of rabbits with 4 legs = 8