 Hello and welcome to the session. In this session we shall study about formula. If we say speed of a car is s and time taken by a car to travel a certain distance d in time t seconds, then we have s is equal to d upon t as the formula for speed statement s is equal to d by t is a formula which expresses briefly what it might take a paragraph to explain. We can say formula is a rule for calculation in the form of an equation using variables and symbols. For example, a is equal to l into b where l is the length of the rectangle, b is the breadth of the rectangle, the rectangle. Similarly, equal to l into b into h where l is the length of the cuboid, b is the breadth of the cuboid, h is the height of the cuboid and v is the volume of the cuboid. Now let us discuss how framing of a formula is done from a given statement. By the use of variables and symbols, the translation of words into an equation is called framing of a formula. For example, one, a number y is seven more than a number x can be written as y is equal to seven plus x second. The product of two numbers that is a into b is equal to c third is two times a number p increased by five is twelve that is plus five is equal to twelve. Now we will discuss changing the subject of a formula. First let us see what is subject of a formula. A subject of a formula is the variable that is expressed in terms of other variables. Suppose if we consider the formula equal to four i is the subject of the formula. Now suppose we want to find the value of the variable i we can change the subject of the formula equal to four i becomes a is equal to p by four by dividing both sides by four. The subject now changes to i from p so i is the subject of the formula. Now consider the following examples f is equal to nine c plus thirty five gives f directly. Subject is f minus thirty five by nine is equal to c this equation solves for c. Now the subject is c now v is equal to i r solves for v directly equal to v by r solves for i equal to v by i solves for r. Now we shall study how to find the value of a variable in a formula. There may be two cases first if we want to find the value of a variable that is subject of a formula the value of the subject of a formula can be found by substituting the given values of other variables solving for the subject. For example if in the formula f is equal to nine c by five plus thirty two and c is given as hundred we get f is equal to nine into hundred by five plus thirty two. That is f is equal to hundred and eighty plus thirty two that is two hundred and twelve so f is equal to two hundred and twelve. Second case is when we want to find the value of a variable that is not the subject of the formula method one could be that we can substitute the given values in the formula and then solve for the variable. For example find the value of t in the equation v is equal to u plus a t where u is equal to two a is equal to ten and v is equal to three. Here we get equal to two plus ten t implies three equal to ten t that is equal to one which implies one by ten method two could be transform the formula first to change the subject to the variable. We wish to find in the example we have v is equal to u plus a t we get minus u is equal to a t that is v minus u upon a is equal to t. Now the subject has changed to t now we substitute the values of v u and a that is equal to three minus two upon ten that is one upon ten so t is equal to one upon ten. This completes our session hope you enjoyed this session.