5)When a number is increase by 32% and then multiplied by 80%,the result is 1.9008.Find the number.
6)Adding 28 to 3 times of a number is equal to 12 added to 5 times the number.Find the number.
7)Mr.Chan had a sum of money.He first used 40% of it and then used 30% of the rest.He then had $210 left.How much did he have originally?
8)In a zoo there are 28 animals with 68 feet.If there are only hens and dogs,find the number of dogs.
EASY MATHS!!
2007-07-30 1:13 am
回答 (2)
2007-07-30 1:24 am
✔ 最佳答案
5. let the number be xx(1+32%)(80%)=1.9008
1.056x=1.9008
x=1.8
6.Let the number be x
3x+(28)=5x+12
2x=16
x=8
7.assume he had $x originally
(1-40%)x(1-30%)=210
0.42x=210
x=500
8.let the number of dogs be x ,so the number of hens be (28-x)
As we know , the number of feet of dog and hen are 4 and 2 respectively
4x+2(28-x)=68
2x+56=68
x=6
2007-07-30 1:32 am
Answers:
5)let the number be x,
(1+32%)x * 0.8=1.9008
x=1.8
6)let it be x,
3x+28=5x+12
2x=16
x=8
7)let $x be the sum of money he had originally,
x*(1-40%)*(1-30%)=210
x*0.6*0.7 =210
0.42x =210
x = 500
He had $500 originally.
8)x+y=28 ----1)
2x+4y=68 ----2)
1)*2, 2x+2y=56 ----3)
2)-3) 4y-2y=12
2y=12
y=6
Substitute y into 1), x+6=28
x=22
the number of dogs is 6 and the number of hens is 22
5)let the number be x,
(1+32%)x * 0.8=1.9008
x=1.8
6)let it be x,
3x+28=5x+12
2x=16
x=8
7)let $x be the sum of money he had originally,
x*(1-40%)*(1-30%)=210
x*0.6*0.7 =210
0.42x =210
x = 500
He had $500 originally.
8)x+y=28 ----1)
2x+4y=68 ----2)
1)*2, 2x+2y=56 ----3)
2)-3) 4y-2y=12
2y=12
y=6
Substitute y into 1), x+6=28
x=22
the number of dogs is 6 and the number of hens is 22
參考: myself
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