BY:BY:POOJA POONIAPOOJA POONIA

VII BVII B

MATHEMATIMATHEMATICSCS

FORMULAEFORMULAE

A relation (equation) A relation (equation) between two or more between two or more quantities is called a quantities is called a formulaformula

Literals are used to Literals are used to represent the quantities represent the quantities in a formulain a formula

EXERCISE 6AEXERCISE 6A1)Form a formula for each of the 1)Form a formula for each of the

following:-following:-

(i) Khushi’s weight is 5 kg more (i) Khushi’s weight is 5 kg more than thrice that of Poojathan thrice that of Pooja

SOLUTION:SOLUTION:

Let Khushi weight be a and and Let Khushi weight be a and and Pooja’s weight bPooja’s weight b

Therefore the formula is, a= 5+3b Therefore the formula is, a= 5+3b

(ii) The volume (v) of a cube is (ii) The volume (v) of a cube is equal to the cube of its side (a) equal to the cube of its side (a)

SOLUTION:SOLUTION:

The volume of a cube = the cube The volume of a cube = the cube of its sides of its sides

v = a*a*av = a*a*a

Therefore v = aTherefore v = a33

(iii) The speed (s) of a body equals (iii) The speed (s) of a body equals the distance covered (d) divided the distance covered (d) divided by time (t).by time (t).

SOLUTION:SOLUTION:

We all know that Speed = distanceWe all know that Speed = distance

________________________________________________________________

timetime

Therefore s = d Therefore s = d _______ _______

t t

2)Express each of the following 2)Express each of the following statement in the form of a statement in the form of a formula :-formula :-

(i) A number (p) multiplied by itself (i) A number (p) multiplied by itself twice is equal to another number twice is equal to another number (q)(q)

SOLUTION:SOLUTION:

p*p*p = qp*p*p = q

Therefore ,pTherefore ,p33 = q = q

((ii) A number (a) exceeds ii) A number (a) exceeds another number (b) by 10.another number (b) by 10.

SOLUTION:SOLUTION:

a exceeds b by 10a exceeds b by 10

Therefore, a=b+10Therefore, a=b+10

(iii) The sum of a number (a) (iii) The sum of a number (a) and 1675 is four times and 1675 is four times another number (b)another number (b)

SOLUTION:SOLUTION:

a + 1675 = b+b+b+ba + 1675 = b+b+b+b

Therefore ,a + 1675 =4bTherefore ,a + 1675 =4b

(iv)Vinay is twice as old as (iv)Vinay is twice as old as VijayVijay

SOLUTION:SOLUTION:

Vinay’s age = xVinay’s age = x

Vijay’s age = yVijay’s age = y

Therefore ,a=2y Therefore ,a=2y

3)Make the given variables 3)Make the given variables the subject of the formula:-the subject of the formula:-

(i) C=5 (F – 32(i) C=5 (F – 32)) ______________

99

SOLUTION:SOLUTION:

9/5 C = F9/5 C = F

Therefore ,Therefore ,

F = 9/5 C +32F = 9/5 C +32

(ii) A = P+ PRT(ii) A = P+ PRT ____________________________

100100

Multiply both the sides by 100Multiply both the sides by 100

A-P=PRTA-P=PRT ______________________________

100100

100(A-P)=PRT100(A-P)=PRT

So,R= 100*(A-P)So,R= 100*(A-P) ____________________________________________________________________________

PTPT