Maths questions??

用戶3541

2006-11-26 7:14 pm

1.) One-fourth of the coins in a bag are $1 coin and the rest are $2 coin. The total value of the coins is $140.Find
(a) The total number of coins in the bag,
(b) the total value of $2 coin.

2.)The number of student in school A is 75% of that in school B.If the two schools have 2800 altogether,find the difference of the number between the schools.

回答 (1)

Ckw＊

2006-11-26 7:51 pm

✔ 最佳答案

1(a).let x be the no. of coins
1*(1/4)x+2*(3/4)x=140
(1/4)x+(6/4)x=140
(7/4)x=140
x=80
therefore, there are 80 coins in the bag.
(b)80*3/4*2
=60*2
=$120

2.let x be the no. of students in school A and
y be the no. of students in school B

x=0.75y--------(1)
x+y=2800---------(2)
from(1), x-0.75y=0--------------(3)
(2)-(3), y-(-0.75y)=2800
1.75y=2800
y=1600
sub. y=1600 into (2),
x+1600=2800
x=1200
therefore the difference of the number between the schools is 1600-1200=400

3.let x be the no. of mangoes she has bought
15x+5=20(x-6)
15x+5=20x-120
-5x=-125
x=25

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