the perimeter of a rectangular field is 140m. If the length is increased by 15m and breadth is decrease by 5m, the length will become 3 times the breadth. Find the length of breadth of the field.

Let x=length; 70-x = breadth

(x + 15) =(3)*((70-x) - 5)
x + 15 = 3 * (65 - x)
x + 15 = 195 - 3x
4x = 180
x = 45
70 - x = 25

To solve this problem, we can set up a system of equations based on the given information.

Let's assume the length of the rectangular field is L and the breadth is B.

According to the first condition, "the perimeter of a rectangular field is 140m," we know that the perimeter of a rectangle is given by the formula: perimeter = 2L + 2B. So, for this rectangular field, we have:

2L + 2B = 140 ---(Equation 1)

According to the second condition, "If the length is increased by 15m and breadth is decreased by 5m, the length will become 3 times the breadth," we can write the following equation:

(L + 15) = 3(B - 5) ---(Equation 2)

Now, we can solve this system of equations to find the values of L and B.

First, let's simplify Equation 2:

L + 15 = 3B - 15

Next, let's rearrange Equation 2:

L - 3B = -30 ---(Equation 3)

Now, we can solve the system of equations by substituting Equation 3 into Equation 1:

2L + 2B = 140
2(3B - 30) + 2B = 140
6B - 60 + 2B = 140
8B = 200
B = 25

Now, we can substitute the value of B back into Equation 3 to find the value of L:

L - 3(25) = -30
L - 75 = -30
L = 45

Therefore, the length of the rectangular field is 45m and the breadth is 25m.