Complete Question
We have a total of 420 students. 2 times 3 times the number of girls is equal to 2 times the number of boys how many girls and how many boys
Answer:
The number of boys = x = 315 boys
The number of girls = y = 105 girls
Step-by-step explanation:
Let
The number of boys = x
The number of girls = y
We have 420 students
2 times 3 times the number of girls is equal to 2 times the number of boys
x + y = 420..... Equation 1
2 × 3y = 2x
6y => 2x
x => 6y/2 = 3y
We substitute 3y for x in Equation 1
3y + y = 420
4y = 420
y =>420/4
y => 105
Solving for x
x = 3y
x = 3 × 105
x = 315
Therefore,
The number of boys = x = 315 boys
The number of girls = y = 105 girls
Where is the multiple choice answers ?
Answer:
The speed of the current is 3 miles per hour
Step-by-step explanation:
The equations for rate (r), distance (d), and time (t) are ⇒ d = rt, r = d/t, = t = d/r
Let x = speed in still water
Let c = speed of the current
The main difference with these problems is rate needs to be expressed using two variables because moving upstream the current is against you and downstream it moves with you.
Distance Rate Time
Upstream x − c
Downstream x + c
The distance column with the numbers from the problem and the value for speed in still water for x.
Distance Rate Time
Upstream 4 5 − c
Downstream 16 5 + c
The column for time using the other two columns knowing that rate, distance ⇒ time = Distance Rate Time
Upstream 4 5 − c
5 − c
4
Downstream 16 5 + c
5 + c
16
“It takes as long …” from the problem means that the two times are equal to each other. So, the equation can be written as:
4/5− c = 16/5 + c ⇒ Solve by cross-multiplying ⇒ 5(4 + c) = 16 5( − c) ⇒ c = 3
