. 30 girls and boys have planned for a picnic. There is a ratio of
3 girls to 7 boys. How many boys are there?
X boys.
3x/7 girls.
x + 3x/7 = 30.
7x + 3x = 210.
10x = 210.
X = 21.
To find the number of boys, we can use the given ratio of 3 girls to 7 boys.
Let's represent the number of girls as "g" and the number of boys as "b".
We know that the ratio of girls to boys is 3:7.
So we can set up the equation:
3/7 = g/b
To find the value of "b" (the number of boys), we can cross-multiply and solve for "b".
3b = 7g
To find the value of "b", we need to know the value of "g".
From the given information, we know that there are a total of 30 girls and boys.
Let's represent the total number of girls and boys as "x".
So we have the equation:
g + b = x
Substituting the given total value:
30 = g + b
Now we can solve the system of equations:
3b = 7g (equation 1)
g + b = 30 (equation 2)
From equation 2, we can solve for "g" in terms of "b":
g = 30 - b
Substituting this into equation 1:
3b = 7(30 - b)
Expanding and simplifying:
3b = 210 - 7b
Combining like terms:
3b + 7b = 210
10b = 210
Dividing both sides by 10:
b = 21
Therefore, there are 21 boys.
To find the number of boys, we first need to determine the ratio between girls and boys.
The given ratio is 3 girls to 7 boys. This can be written as 3:7, where 3 represents the number of girls and 7 represents the number of boys.
Next, we need to find the value of each ratio unit. This can be done by dividing the total number of parts (in this case, 10 parts: 3 + 7) by the number of parts representing boys (7 parts).
So, each ratio unit represents 10 parts divided by 7 parts, which is approximately 1.42857.
To find the number of boys, we multiply the number of ratio units by the value of each unit. In this case, we multiply 1.42857 by 7, resulting in approximately 10 boys.
Therefore, there are approximately 10 boys planned for the picnic.