(a) mathematical symbols and variables
(b) given conditions, and(c) simplification.
Some well known formulae are listed below:Area of a rectangle A = l x b
A = Areal = Length
b = BreadthPerimeter of a rectangle P = 2(l + b)
P = PerimeterVolume of a cuboid V = l x b x h
V = Volumeh = height
Simple interest
P = Principal
T = TimeR = Rate percent per annum
In an n-sided polygon, the number of diagonals d, which can be drawn from one vertex, is 3 less than the number of sides of the polygon. Write this as a formula. Express d in terms of n.
Number of diagonals = d
Number of sides of a polygon = n
the required formula is = d = n -3
The sum of the reciprocal of x and the reciprocal of y equals the reciprocal of m. Express this as a formula.
Reciprocal of 
Reciprocal of 
Their total weight = px kg
Their total weight = qy kg
Total weight of [p + q] students = [px + qy] kg
Average weight of [p + q] students 
A number of two digits p and q in that order is 7 greater than the number formed by reversing the digits.
The ten's digit is p and the unit's digit is q.
Then the number is 10p + q.The number formed by reversing the digits = 10q + p
(10p + q) - (10q + p) = 7
(1) ? a x
(2) b ? yIn the first case, the man walks at x km/hr for 'a' hours, so he covers a distance of (xa) kilometres. In the second case, he cycles for 'b' kilometres at a speed of y km/hr, so he takes (b/y) hours.
the total distance he covers = (xa + b) and
the total time he takes 
Average speed 
