F1 Math Question
2009-03-08 8:49 pm
Tom is asked to go buy some blue, red and orange balloons from the party supplies store. Unfortunately, by the time he gets to the store, he completely forgets how many of each colour he is supposed to buy. All he can remember is that he is told to buy a total of 100 balloons and the total number of blue ones should be three times of the total number of red ones. He is given an exact amount of money $745 for them. He also knows that the blue, red and orange balloons cost $9, $4 and $7 each, respectively. How many balloons of each colour was he asked to buy?
回答 (2)
2009-03-08 9:00 pm
✔ 最佳答案
Let num of Blue = xnum of red = y
num of orange = z
1. x + y + z = 100
2. x = 3y
3. 745 = 9x + 4y + 7z
From 1 and 2 we get:
4y + z = 100
4. z = 100 - 4y
From 2 and 3 we get:
745 = 27y + 4y +7z
5. 745 = 31y + 7z
From 4 and 5 we get:
745 = 31y + 7(100 - 4y)
745 = 31y + 700 -28y
45 = 3y
6. y = 15
From 2 and 6 we get:
x = 3 X 15
7. x = 45
From 1, 6 and 7 we get:
45 + 15 + z = 100
z = 40
So there are 45 blue, 15 red and 40 orange balloons.
2009-03-08 9:04 pm
Let R red balloons was he asked to buy, then he should buy 3R blue balloons , and he should buy 100 - R - 3R = 100 - 4R orange balloons.
we have 9(3R) + 4R + 7(100- 4R) = 745
27R + 4R + 700 - 28R = 745
3R = 45
R = 15
So 15 red , 15*3= 45 blue and 100 - 4*15 = 40 orange balloons was he asked to buy.
we have 9(3R) + 4R + 7(100- 4R) = 745
27R + 4R + 700 - 28R = 745
3R = 45
R = 15
So 15 red , 15*3= 45 blue and 100 - 4*15 = 40 orange balloons was he asked to buy.
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