F 2數學題...共2題...

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2008-11-19 6:07 am

Two unknowns....
Applications of Simultaneous Linear Equations in Two Unknowns

1.A farmer has pigs and ducks.Among the pigs and ducks there are 24 heads and 64 feet.How many pigs and how amny ducks are there?

2.Roy has x pieces of $5 and y pieces of $1 coins, giving a total of $40. If there are 12 coins altogether, find the values of x and y.

回答 (1)

2008-11-19 6:20 am

✔ 最佳答案

ans:

1)
let x be the number of pigs
y be the number of ducks

then we have
x+y=24 ..........(1)
4x+2y=64 .......(2)

solving the simultaneous equations
4 times (1) minus (2)... 2y=32 , so y=16 ....(3)
subsitute (3) into (1)... x+16=24, so x=8

so answer is, 8 pigs and 16 ducks.

2)
we have,
5x+y=40 ........(1)
x+y=12 ..........(2)

solving the simultaneous equations,
(1) minus (2) ... 4x=28, so x=7 ........(3)
subsitute (3) into (2) ... 7+y=12, so y=5

so answer is, 7 $5 coins and 5 $1 coins

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