請解決下列這兩題數學題,加運算步驟

1.A is greater than B by 20%;B is less than C by 8%.By how much percent is A greater than C?

A is greater than B by 20%, therefore A = 1.2B
B is less than C by 8%, therefore B = 0.92C

A = 1.2B = 1.2 (0.92C) = 1.104C
So, A is greater than C by 10.4%

2.Find the least number which when divided respectively by 14,19,21 leave remainders 11,16 and 18.

Let x be the requested number.

When x divided by 14, the remainder is 11.
i.e. x+3 is divisible by 14.

When x divided by 19, the remainder is 16.
i.e. x+3 is divisible by 19.

When x divided by 21, the remainder is 18.
i.e. x+3 is divisible by 21.

Now, find the LCM of 14, 19 & 21.
14 = 2*7
19 = 19
21 = 3*7
The LCM of 14, 19, 21 is 2*7*19*3 = 798

The least possible vaule of x+3 is 798.
Therefore, 795 is the least number which when divided respectively by 14, 19, 21 leave remainders 11, 16 and 18.

3.The dimensions of a rectangular field,correct to the nearest 5 metres are 80m X 45m.Find maximum possible area of the field.

Length of the field = 80m (correct to the nearest 5 meters)
i.e. Length of the field ≦ 82.5

Width of the field = 45m (correct to the nearest 5 meters)
i.e. Width of the field ≦ 47.5

The maximum possible area of the field = 82.5 * 47.5 = 3918.75 m²

設a的數值為x,
a:b=x:0.8x
a:b=5:4

b:c=0.8x:(0.8)(1+0.08)x
b:c=25:27

a:b =5:4
b:c= 25:27
--------------------------
A:B:C=125:100:108

SO A/C=125:108=1.157.....

3.5^2=25m^2