有2題數學唔識做
A) 我有一D10蚊和5蚊的銀仔,加埋總共145蚊,請問我有幾多個10蚊,幾多個5蚊銀?
B) 有8組汽水罐:
第一組有2排,每排有3個,總共6個
第二組有4排,每排有6個,總共24個
第三組有8排,每排有12個,總共96個
咁第8組會有幾多個?
我計過,只要將6X4=24 24X4=96 96X4........乘到第8次,就係98304,而正確答案都係98304,不過我要用代數列式(A也是),
請幫忙,答案我知道,但不知怎麼列式,這是我朋友的妹妹的功課,雖然我不用交,但我自己也很想知道答案,THX
grade 7 maths代數10點!!!!
2010-11-30 8:30 pm
回答 (2)
2010-11-30 9:11 pm
✔ 最佳答案
sol1)
to let you have x coins of 10$ and y coins for 5$
二元一次不等式
145>10x+5y
145>5(2x+y)
29>2x+y
at least you have 27 coins of 5$ and one 10$ coin
2)
group 4 has 16 lines,each line has 24 seats,so there are 384 seats
so to sum up that the group n there are 2^n lines,each line has 3*2^(n-1) seats,therefore there are 2^n*3*2^(n-1) seats,iq 3*2^(2n-1) seats
to sum up in group 8
3*2^(16-1)
=98304 seats
2010-11-30 13:11:43 補充：
another ans is 14 coins of 10$ and one 5$ coin
2010-11-30 19:56:07 補充：
有公式阿xd
參考: google
2010-12-01 2:11 am
a) Let x be the number of $10 coins. Let y be the number of $5 coins.
x+y=145
Because x and y MUST be positive integer or zero,
so sub. x be the positive integer or zero, when y is positive integer or zero.
{x,y}=
{0,29};{1,27};{2,25};{3,23};{4,21};{5,19},{6,17},{7,15};{8,13};{9,11};{10,9};
{11,7};{12,5};{13,3};{14,1}
b) Let n be the group number of the can.
The number of row of can = 2^n. The number of can in a row = 3*2^(n-1)
So the total number of can = 3*2^(2n-1)
Sub. n=8 into the equation.
3*2^(2(8)-1)
=3*2^15
=3*32768
=98304
x+y=145
Because x and y MUST be positive integer or zero,
so sub. x be the positive integer or zero, when y is positive integer or zero.
{x,y}=
{0,29};{1,27};{2,25};{3,23};{4,21};{5,19},{6,17},{7,15};{8,13};{9,11};{10,9};
{11,7};{12,5};{13,3};{14,1}
b) Let n be the group number of the can.
The number of row of can = 2^n. The number of can in a row = 3*2^(n-1)
So the total number of can = 3*2^(2n-1)
Sub. n=8 into the equation.
3*2^(2(8)-1)
=3*2^15
=3*32768
=98304
收錄日期: 2021-04-13 17:41:00
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20101130000051KK00367