中一數學題請幫忙, 謝謝! 急!

donald63

1.Find the H.C.Fof the following pairs of numbers.
a. 2 x 3 x 5.3 x 5 x 7
b. 3(2次方) x 7.2(3次方) X 5  

2. Find the L.C.M.of the following pairs of numbers.
a. 2 X 5(2次方) x 11.2(2次方) x 5(3次方)
b. 3(2次方) x7(2次方) , 2(2次方) x 5


3 .It is known that the H.C.F of a given number and 28 is 2. Find two possible values of the given number,

4. It is known that the L.C.M of a given number and 18 is 72. Fing two possible values of the given number.


要步驟及答案, 謝謝!

comingbb

The H.C.F. of  2 x 3 x 5 and 3 x 5 x 7 = 3 x 5 = 15
The H.C.F. of 3(2次方) x 7 and 2(3次方) X 5 = 1

The L.C.M. of 2 X 5(2次方) x 11 and 2(2次方) x 5(3次方)
= 2(2次方)  x 5(3次方) x 11
= 4 x 125 x 11 = 5500

The L.C.M. of 3(2次方) x7(2次方) and 2(2次方) x 5
= 2(2次方) x 3(2次方) x 5 x 7(2次方)
= 4 x 9 x 5 x 49 = 8820

Q3 It is known that the H.C.F of a given number and 28 is 2. Find two possible values of the given number,
28 = 2 x 2 x 7
10 = 2 x 5
22 = 2 x 11
The H.C.F. of 10 and 28 is 2
The H.C.F. of 22 and 28 is 2
The possible two values are 10, 22

Q4. It is known that the L.C.M of a given number and 18 is 72. Fing two possible values of the given number.
72 = 2 x 2 x 2 x 3 x 3
18 = 2 x 3 x 3
8 = 2 x 2 x 2
24 = 2 x 2 x 2 x 3
The L.C.M. of 8 and 18 is 72
The L.C.M. of 24 and 18 is 72
The possible two values are 8 and 24

donald63

謝謝!
我想請問 3(2次方) x 7 and 2(3次方) X 5 = 1
這條為何是1, 可否詳細說明, 謝謝!   

cp2004

回覆 donald63 的帖子

因為最大HCF 只得 1.

cp2004

回覆 donald63 的帖子

1x 3(2次方) x 7

1X 2(3次方) X 5

見到1 其實是要自己記得加上去

donald63

唔該晒