Ray's weight is 3 times the weight of his sister. His dad weighs twice as much as Ray. Their total weight is 400 pounds. How much does each person weigh?

What does this problem teach you about physics? Nothing.

Use algebra.
R = Ray's weight
S = Sis' weight
D = Dad's weight

R = 3S
D = 2R = 6S

S + 3S + 6S = 10S = 400

Take it from there.

To find out how much each person weighs, let's set up equations based on the given information.

Let's assume Ray's sister's weight is "x" pounds.

According to the problem, Ray's weight is 3 times the weight of his sister, so Ray's weight would be 3x pounds.

The problem also states that their dad weighs twice as much as Ray, so their dad's weight would be 2 * (3x) = 6x pounds.

Finally, the total weight of the three individuals is 400 pounds, so we can set up the equation: x + 3x + 6x = 400.

Combining like terms, the equation becomes 10x = 400.

Now, we can solve for x by dividing both sides of the equation by 10: x = 400 / 10 = 40.

So, Ray's sister weighs 40 pounds, Ray weighs 3 * 40 = 120 pounds, and their dad weighs 6 * 40 = 240 pounds.

Hence, Ray's sister weighs 40 pounds, Ray weighs 120 pounds, and their dad weighs 240 pounds.