Selina solutions concise mathematics class 6 icse Solutions for Chapter 21 framing algebraic expressions including evaluation

Exercises in Chapter 21 framing algebraic expressions including evaluation Grade 6

Exercise 21

Questions in Exercise 21

Q1) Write in the form of an algebraic expression :

(i) Perimeter (P) of a rectangle is two times the sum of its length (l) and its breadth (b).

(ii) Perimeter (P) of a square is four times its side.

(iii) Area of a square is square of its side.

(iv) Surface area of a cube is six times the square of its edge.

Q2) Express each of the following as an algebraic expression :

(i) The sum of x and y minus m.

(ii) The product of x and y divided by m.

(iii) The subtraction of 5m from 3n and then adding 9p to it.

(iv) The product of 12, x, y and z minus the product of 5, m and n.

(v) Sum of p and 2r – s minus sum of a and 3n + 4x

Q3) Construct a formula for the following :

Total wages (₹ W) of a man whose basic wage is (₹ B) for t hours week plus (₹ R) per hour, if he Works a total of T hours.

Q4) If x = 4,evaluate :

(i) 3x + 8

$(ii)\ x^2-2x$

$(iii)\ \frac{x^2}{\ 2}$

Q5) If m – 6, evaluate :

(i) 5m – 6

$(ii)2m^2+3m$

$(iii)(2m)^2$

Q6) If x = 4, evaluate :

(i) 12x + 7

$(ii)\ 5x^2+4x$

$(iii)\ \frac{x^2}{8}$

Q7) If m = 2, evaluate :

(i) 16m – 7

$(ii)\ 15m^2-10m$

$(iii)\ \frac{1}{4}\times m^3$

Q8) If x = 10, evaluate :

(i) 100x + 225

$(ii)\ 6x^2-25x$

$(iii)\ \frac{1}{50}\times x^3$

Q9) If a = – 10, evaluate :

(i) 5a

$(ii)\ a^2$

$(iii)\ a^3$

Q10) If x = – 6, evaluate :

(i) 11x

$(ii)4x^2$

$(iii)2x^3$

Q11)If m = – 7, evaluate :

(i) 12m

$(ii)2m^2$

$(iii)2m^3$

Q12) Find the average (A) of four quantities p, q, r and s. If A = 6, p = 3, q = 5 and r = 7 ; find the value of s.

Q13) If a = 5 and b = 6, evaluate :

(i) 3ab

$(ii)\ 6a^2b$

$(iii)\ 2b^2$

Q14) If x = 8 and y = 2, evaluate :

(i) 9xy

$(ii)\ 5x^2y$

$(iii)\ (4y)^2$

Q15) If x = 5 and y = 4, evaluate :

(i) 8xy

$(ii)\ 3x^2y$

$(iii)\ 3y^2$

Q16) If y = 5 and z = 2, evaluate :

(i) 100yz

$(ii)\ 9y^2z$

$(iii)\ 5y^2$

$iv)\ (5z)^3$

Q17) If x = 2 and y = 10, evaluate :

(i) 30xy

$(ii)\ 50\times y^2$

$(iii)\ (10x)^2$

$(iv)\ 5y^2$

Q18) If m = 3 and n = 7, evaluate :

(i) 12mn

$(ii)\ 5mn^2$

$(iii)\ (10m)^2$

$(iv)\ 4n^2$

Q19) If a = -10, evaluate :

(i) 3a – 2

$(ii)\ a^2+8a$

$(iii)\ \frac{1}{5}\times a^2$

Q20) If x = -6, evaluate :

(i) 4x – 9

$(ii)\ 3x^2+8x$

$(iii)\ \frac{x^2}{2}$

Q21) If m = -8, evaluate :

(i) 2m + 21

$(ii)\ m^2+9m$

$(iii)\ \frac{m^2}{4}$

Q22) If p = -10, evaluate :

(i) 6p + 50

$(ii)\ 3p^2-20p$

$(iii)\ \frac{p^2}{50}$

Q23) If y = -8, evaluate :

(i) 6y + 53

$(ii)\ y^2+12y$

$(iii)\ \frac{y^3}{4}$

Q24) If x = 2 and 7 = -4, evaluate :

(i) 11xy

$(ii)\ 5x^2y$

$(iii)\ (5y)^2$

$(iv)\ 8x^2$

Q25) If m = 9 and n = -2, evaluate

(i) 4mn

$\left(ii\right)\ 2m^2n$

$(iii)\ (2n)^3$

Q26) If m = -8 and n = -2, evaluate :

(i) 12mn

$(ii)\ 3m^2n$

$(iii)\ (4n)^3$

Q27) If x = -5 and y = -8, evaluate :

(i) 4xy

$(ii)\ 2xy^2$

$(iii)\ 4x^2$

$(iv)\ 3y^2$

Q28) Find T, if T = 2a – b, a = 7 and b = 3.

Q29) From the formula $B=2a^2-b^2$ calculate the value of B when a = 3 and b = -1.

Q30) The wages ₹ W of a man earning ₹ x per hour for t hours are given by the formula W = xt. Find his wages for working 40 hours at a rate of ₹ 39.45 per hour.

Q31) The temperature in Fahrenheit scale is represented by F and the temperature in Celsius scale is represented by C. If F = 9/5 x C + 32, find F when C = 40.