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There are 30 flowers. Some have 3 petals and some have 4 petals.All the flowers together have 102 petals. How many flowers have 4 petals?

 Aug 31, 2020
 #1
avatar+783 
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Let x be the number of flowers with 3 petals and 30-x the number of flowers with 4 petals. We form an equation:

 

3x+4(30-x)=102

3x+120-4x=102

-x+120=102

-x=-18

x=18 3 petal flowers,

 

So there are 30-18=12 4 petal flowers.

 Aug 31, 2020
 #2
avatar+1039 
+1

You never know when you will need system of equation!

 

The the number of 3-petal flowers be x, and the number of 4-petal flowers be y.

 

from here, we know that:

 

x + y = 30

3x + 4y = 102

 

Using substitution, we see that:

x = 30 - y

3(30 - y) + 4y = 102

90 - 3y + 4y = 102

90 + y = 102

y = 12

 

Here are some 4 pétaled flowers for you:

 

 

:)

 Aug 31, 2020

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