

[?]Subscribe To This Site

Change the Subject of a Formula
Subject of the formula:It is a variable which is expressed in terms of other variables involved in the formula.Formulas are written so that a single variable, the subject of the formula is on the L.H.S. of the equation. Everything else goes on the right side of the equation. We evaluate the formula by substituting for the literal numbers on the right hand side. For example: In the formula v = u + at, v is the subject. To find v in the example, we substitute the values u, a and t in the R.H.S. of the equation. Changing the subject of the formula:To change the subject of a formula, begin with the variable to become the new subject, and apply inverse operation as for solving equations in the opposite order to the order conventions. 1. To make ‘u’ the subject of the formula in v = u + at, 2. To make ‘t’ the subject of the formula, v = u + at, Solved examples to change the subject of a formula1. The volume of a cuboid is the product of length and breadth of the cuboid.Solution: If l, b, h are length, breadth and height of the cuboid. Also, if the volume is denoted by v then V = l × b × h or, l = V/(b × h) Here, the subject is l. or, b = V/(l × h) Here, the subject is b. or, h = V/(l × b) Here, the subject is h. 2. In the relation C/5 = make (F  32)/9 make F as the subject. Solution: C/5 = (F  32)/9 ⇒ 9C/5 = F  32 ⇒ 9C/5 + 32 = F ⇒ F = 9C/5 + 32 3. Make y the subject of the formula x = (y + z)/(y  z) Solution: x = (y + z)/(y  z) x (y  z) = y + z [multiply both sides by (y  z)] xy – xz = y + z xy  y = z + zx y (x  1) = z (x + 1) y = z(x + 1)/(x  1) More workedout problems to change the subject of a formula4. Write the formula for finding the area of the rectangle and indicate the subject in this formula. Also, make l as the subject. If A = 42 cm^{2} and b = 6 cm, then find l. Solution: If area is denoted by A, length by l and breadth by b, 5. For a right angled triangle, square of the hypotenuse (h) is equal to the sum of squares of its other two sides (p, b). • Also, make ‘p’ the subject of the formula and find p if h = 10 and Solution: h^{2} = 25 Changing the subject, 6. In the formula, l = a + (n  1)d make d as the subject. Find d when
● Formula  Worksheets
7th Grade Math Problems


