the length of a rectangle is 3 times its breadth,if the perimeter is 84 , find the length

L = 3B

2L + 2B = 2(3B) + 2B = 84

Solve for B, then L.

10.5

To find the length of the rectangle, we need to set up a system of equations using the given information.

Let's assume that the breadth of the rectangle is x.

According to the given information, the length of the rectangle is 3 times its breadth. Therefore, the length would be 3x.

The perimeter of a rectangle is calculated by adding the lengths of all its sides. For a rectangle, the perimeter is given by the formula: P = 2(length + breadth).

In this case, the perimeter is given as 84, so we can set up the equation: 84 = 2(3x + x).

Simplifying this equation, we get: 84 = 2(4x).

Next, we can remove the parentheses by multiplying 2 with (4x): 84 = 8x.

Now, to solve for x, we divide both sides of the equation by 8: x = 84/8.

Simplifying this further, we have: x = 10.5.

Therefore, the breadth of the rectangle is 10.5.

Since the length is 3 times the breadth, the length would be 3 * 10.5 = 31.5.

So, the length of the rectangle is 31.5 units.